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  • 1. Adamus, Grazyna
    et al.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kowalczuk, Marek
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    MALDI-TOF MS Reveals the Molecular Level Structures of Different Hydrophilic-Hydrophobic Polyether-esters2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 6, 1540-1546 p.Article in journal (Refereed)
    Abstract [en]

    Multi- and triblock copolymers based on 1,5-dioxepan-2-one/epsilon-caprolactone (DXO/CL) were investigated by MALDI-TOF MS to determine the influence of copolymer composition and architecture on the molecular structures at the individual chain level. The copolymer compositions, average block lengths, and molecular weights were determined by H-1 and C-13 NMR and by SEC, respectively. The structures of polyether-ester oligomers (linear, cyclic) as well as the chemical structures of their end groups were established on the basis of their MALDI-TOF mass spectra. The mass spectrum of PDXO homopolymer was relatively simple, however, complex mass spectra were obtained in the case of multi- and triblock copolymers and the mass spectra clearly discerned the molecular level effect of copolymer composition and copolymer type.

  • 2. Adekunle, Kayode
    et al.
    Cho, Sung-Woo
    Patzelt, Christian
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Skrifvars, Mikael
    Impact and flexural properties of flax fabrics and Lyocell fiber-reinforced bio-based thermoset2011In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 30, no 8, 685-697 p.Article in journal (Refereed)
    Abstract [en]

    A bio-based thermoset resin was reinforced with flax fabrics and Lyocell fiber. The effect of different weave architectures was studied with four flax fabrics with different architectures: plain, twill (two different types), and dobby. The effect of the outer ply thickness was studied and characterized with flexural and impact testing. Composites manufactured with plain weave reinforcement had the best mechanical properties. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were 280MPa, 32GPa, 250MPa, 25GPa, and 75 kJ/m (2), respectively. Reinforcements with twill-weave architecture did not impart appreciable flexural strength or flexural modulus even when the outer thickness was increased. Plain- and dobby (basket woven style)-weave architectures gave better reinforcing effects and the flexural properties increased with an increase in outer thickness. Water absorption properties of the composites were studied and it was observed that the hybridization with Lyocell fiber reduced the water uptake. Field-emission scanning electron microscopy was used to study the micro-structural properties of the composites.

  • 3.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Biobased Composites Prepared by Compression Molding with a Novel Thermoset Resin from Soybean Oil and a Natural-Fiber Reinforcement2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 116, no 3, 1759-1765 p.Article in journal (Refereed)
    Abstract [en]

    Biobased composites were manufactured with a compression-molding technique. Novel thermoset resins from soybean oil were used as a matrix, and flax fibers were used as reinforcements. The air-laid fibers were stacked randomly, the woven fabrics were stacked crosswise (0/90 ), and impregnation was performed manually. The fiber/resin ratio was 60 : 40. The prepared biobased composites were characterized by impact and flexural testing. Scanning electron microscopy of knife-cut cross sections of the specimens was also done to investigate the fiber–matrix interface. Thermogravimetric analysis of the composites was carried out to provide indications of thermal stability. Three resins from soybean oil [methacrylated soybean oil, methacrylic anhydride modified soybean oil (MMSO), and acetic anhydride modified soybean oil] were used as matrices. The impact strength of the composites with MMSO resin reinforced with air-laid flax fibers was 24 kJ/m2, whereas that of the MMSO resin reinforced with woven flax fabric was between 24 and 29 kJ/m2. The flexural strength of the MMSO resin reinforced with air-laid flax fibers was between 83 and 118 MPa, and the flexural modulus was between 4 and 6 GPa, whereas the flexural strength of the MMSO resin reinforced with woven fabric was between 90 and 110 MPa, and the flexural modulus was between 4.87 and 6.1 GPa.

  • 4.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthetic modification of reactive soybean oils for use as biobased thermoset resins in structural natural fiber composites2008In: Polymer Preprints, ISSN 0551-4657, Vol. 49, no 1, 279- p.Article in journal (Refereed)
  • 5.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthesis of reactive soybean oils for use as biobased thermoset resins in structural natural fibre composites2008Conference paper (Refereed)
  • 6.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Preparation of biobased composites using novel thermoset polymers from soybean oil and a natural fibre reinforcement2009Conference paper (Other academic)
    Abstract [en]

    Health related issues, stringent environmental protection policies, search for cost effective and alternative materials, crave for renewability and sustainability and quest for high performance materials for structural applications give the motivation for research in polymer composites and material science. Due to the health, safety and environmental concerns over the conventional synthetic materials and the legislation against their usage both in domestic and industrial applications, alternatives sources that will be comparable in properties are being sought. There is an emerging market for biodegradable polymers which is expected to increase substantially in the coming years.[1] Preparation of Composites Airlaid and woven flax fibre mats were first treated with 4% sodium hydroxide solution for one hour and then washed with plenty of water. This was done in order to remove any residual impurities. The fibres were dried at room temperature for 24 hr and then dried in a vacuum oven for 1hr at a temperature of 105°С. The 8 sheets of the fibre were hand laid cross- wisely and the impregnation was done manually. The fibre/ resin ratio was about 60% to 40%. Methacrylated soybean oil, methacrylic anhydride and acetic anhydride modified soybean oil were the synthesized matrices used. The compression moulding was done at a temperature of 170°С for 5 min at 40bar. Characterisations The tensile testing was performed based on an ISO-test method for tensile tests on plastic materials. The Charpy impact strength of unnotched specimens was evaluated in accordance with ISO 179 using a Zwick test instrument and scanning electron microscopy analysis was done on the fractured specimens. The composites showed various mechanical properties, having impact strengths between 24 and 63 kJ/m² and tensile strength up to 51MPa.

  • 7.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthetic modification of reactive soybean oils for use as biobased thermoset resins in structural natural fiber composites2008Conference paper (Other academic)
  • 8.
    Ajalloueian, Fatemeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Zeiai, S.
    Fossum, M.
    Hilborn, Jöns
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    A bedside collagen-PLGA nanofibrous construct for autologous transplantation of minced bladder mucosal2012In: Journal of Tissue Engineering and Regenerative Medicine, ISSN 1932-6254, Vol. 6, no suppl 1, 128-128 p.Article in journal (Other academic)
    Abstract [en]

    Introduction: Bladder regeneration using minced bladder mucosa is an alternative to costly and time-consuming conventional in vitro culturing of urothelial cells. In this method, the uroepithelium expands in vivo and the patient body appears as an incubator. With our preliminary successes, designing an appropriate scaffold that supports in vivo cell expansion and surgical handling in a clinical setting was our aim. This study, investigates cell expansion in a hybrid construct of collagen/poly (lactic-co-glycolide)(PLGA).

    Materials and methods: An electrospun PLGA mat was placed on a semi-gel collagen inside a mold and covered with a second collagen layer. After gel formation, minced particles of pig bladder mucosa were seeded on the hybrid construct and then processed by plastic compression (PC). The scaffolds were incubated for 2, 4 and 6 weeks in vitro for further studies.

    Results: Tensile tests show an increase in tensile strength of 0.6 ± 0.1 MPa in PC collagen to 3.6 ± 1.1 MPa in hybrid construct. Morphological studies, histological staining and SEM show that the construct has kept its integrity during the time and proliferated urothelial cells have reached confluence after 4 weeks and a multi-layered urothelium after 6 weeks.

    Conclusion: We have designed a mechanically robust scaffold that permits surgical handling and tissue expansion in vivo. The construct is easy-to-use for clinical application in an ordinary surgical operating theater for bladder regeneration.

  • 9.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Brana, M. T. Conde
    Bellander, M.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Deterioration of acrylonitrile butadiene rubber in rapeseed biodiesel2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 111, 211-222 p.Article in journal (Refereed)
    Abstract [en]

    The deterioration of acrylonitrile butadiene rubber (NBR) exposed to rapeseed biodiesel at 90 degrees C was studied. The oxidation of biodiesel and NBR during ageing was monitored by H-1 NMR and infrared spectroscopy, HPLC and titration methods. The oxidation of biodiesel was impeded in the presence of NBR, but promoted in biodiesel-exposed rubber. This was explained as being due to the migration of stabilizer from the rubber to biodiesel, the diffusion of dissolved oxygen from biodiesel into NBR and the absorption of oxidation precursors of biodiesel by the rubber. The resemblance between the anomalous sorption kinetics of biodiesel in NBR and the equilibrium benzene uptake by the aged rubbers revealed that biodiesel caused a network defect in NBR, resulting in a gradual increase in the equilibrium swelling. The cleavage of crosslinks was implausible since the Young's modulus of the rubber at low strains, disregarding an initial decrease, increased with increasing exposure time. The appearance of 'naked' carbon black particles in the scanning electron micrographs of the aged rubbers and a drastic decrease in the strain-at-break of NBR after exposure to biodiesel suggests that internal cavitation was caused by the attack of biodiesel on the acrylonitrile units of NBR.

  • 10.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sjöstedt, C.
    Bellander, M.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Degradation of carbon-black-filled acrylonitrile butadiene rubber in alternative fuels: Transesterified and hydrotreated vegetable oils2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 123, 69-79 p.Article in journal (Refereed)
    Abstract [en]

    The deterioration of acrylonitrile butadiene rubber (NBR), a common sealing material in automobile fuel systems, when exposed to rapeseed biodiesel and hydrotreated vegetable oil (HVO) was studied. The fuel sorption was hindered in HVO-exposed rubber by the steric constraints of bulky HVO molecules, but it was promoted in biodiesel-exposed rubber by fuel-driven cavitation in the NBR and by the increase in diffusivity of biodiesel after oxidation. The absence of a tan δ peak of the bound rubber and the appearance of carbon black particles devoid of rubber suggested that the cavitation was made possible in biodiesel-aged rubber by the detachment of bound rubber from particle surfaces. The HVO-exposed NBR showed a small decrease in strain-at-break due to the migration of plasticizer from the rubber, and a small increase in the Young’s modulus due to oxidative crosslinking. A drastic decrease in extensibility and Payne-effect amplitude of NBR on exposure to biodiesel was explained as being due to the damage caused by biodiesel to the continuous network of bound rubber-carbon black. A decrease in the ZnO crystal size with increasing exposure time suggested that the particles are gradually dissolved in the acidic components of oxidized biodiesel. The Zn2+ cations released from the dissolution of ZnO particles in biodiesel promoted the hydrolysis of the nitrile groups of NBR.

  • 11.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Long-Term Properties of Polyolefins2004Collection (editor) (Refereed)
    Abstract [en]

    We dedicate the current volume entitled "Long-Term Properties of Polyolefins"to Professor Kausch on his 25th anniversary as editor of Advances in PolymerScience. Professor Kausch pioneered the work on molecular effects in thefracture of polymers. This is beautifully summarized in his books on polymerfracture. Professor Kausch is also the perfect gentleman - always eager to helpnewcomers to make their entrance into the scientific community and to assisthis colleagues in their work and accomplishments. With his work, ProfessorKausch has demonstrated the importance of "source science" - to present newdata - and to present reviews of previously published material. This book ispresented in the spirit of Professor Kausch, namely showing a good selection ofdata and explaining what they mean.The main focus of this book is the relation between structure and propertiesand the trend towards better quality and reproducibility. The first chapterdescribes the metallocene polymerisation catalysts and their possihility notonly of tailoring polymer properties but also of manufacturing entirely newmaterials. Due to improved control of microstructure, it will also be possible toproduce specialty polyolefins which could compete with non-olefinic polymers.The next chapter shows how in each new development step catalyst and processinnovations have gone hand in hand and how the control over polymer structureand the ability to tailor material properties has increased. For a betterunderstanding of properties and behaviour, the basic of morphology is fundamentaland is described in chapter three, followed by chapter four aboutfracture properties and microdeformation behaviour. Promising model systemsfor the investigations of the relations between crack-tip deformation, fractureand molecular structure are also presented. Chapter five gives an overviewof stabilization of polyethylene crucial for long-term properties. Two mainapproaches have been used; the first advocates the use of biological antioxidants,and the second relies on the use of reactive antioxidants that are chemicallyattached onto the polymer backbone for greater performance and safety.Chemiluminescence is presented as a too1 for studying the initial stages inoxidative degradation and is explained in chapter six. However, for many years,tailor-made structures specially designed for environmental degradation havealso been a reality. One of the key questions for successhl development and useof environmentally degradable polymers is the interaction between the degradationprodncts and nature and this is illustrated in chapter seven. The developmentof chromatographic methods and use of chromatographic fingerprintinggives not only degradation products bnt also information about degradationmechanisms as well as interaction between the polymer and different environments.The obstacles and possibilities for recycling of polyolefins are discussedin chapter eigbt with special emphasis on analytical methods useful in theqnality concept. It is also shown how recycled material could be a valuable resourcein the Future together with renewable resources. Finally, chapter ninegives examples of existing as we11 as emerging techniques of surface modificationof polyethylene.These chapters together will hopefuiiy inspire to a new generation of polyethyleneby mimicking nature and use of new molecular architecture, newmorphology and also "activated" additives in microdomains, with even morereproducible properties within oarrow limits and with predetermined lifetimes.

  • 12.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Novel release systems from biodegradable polymers1998In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, American Chemical Society (ACS), 1998Conference paper (Refereed)
  • 13.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    New matrices for controlled drug delivery.2000In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, American Chemical Society (ACS), 2000Conference paper (Refereed)
  • 14.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Källrot, Martina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Surface modification of degradable polymers2005In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, American Chemical Society (ACS), 2005Conference paper (Refereed)
  • 15.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Varma, Indra Kumari
    Centre for Polymer Science and Engineering, Indian Institute of Technology, Dehli, India.
    Synthesis, Chemistry and Properties of Hemicelluloses2011In: Biopolymers: New Materials for Sustainable Films and Coatings / [ed] David Plackett, Chichester: John Wiley & Sons, 2011, 1, 135-150 p.Chapter in book (Other academic)
  • 16.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Degradable polymers with tailored properties for biomedical materials2009In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 238Article in journal (Other academic)
  • 17.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Groning, M.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Emission of volatiles from polymers - A new approach for understanding polymer degradation2006In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 14, no 1, 8-13 p.Article in journal (Refereed)
    Abstract [en]

    Emission of low molar mass compounds from different polymeric materials was determined and the results from the volatile analysis were applied to predict the degree of degradation and long-term properties, to determine degradation rates and mechanisms, to differentiate between biotic and abiotic degradation and for quality control work. Solid-phase microextraction and solid-phase extraction together with GC-MS were applied to identify and quantify the low molar mass compounds. Volatiles were released and monitored at early stages of degradation before any matrix changes were observed by e.g. SEC, DSC and tensile testing. The analysis of volatiles can thus also be applied to detect small differences between polymeric materials and their susceptibility to degradation. The formation of certain degradation products correlated with the changes taking place in the polymer matrix, these indicator products could, thus, be analysed to rapidly predict the degree of degradation in the polymer matrix and further to predict the long-term properties and remaining lifetime of the product.

  • 18.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Kumari Varma, Indra
    Centre for Polymer Science and Engineering, Indian Institute of Technology, New Dehli, India.
    Srivastava, Rajiv K.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Polyesters from Large Lactones2009In: Handbook of Ring-Opening Polymerization / [ed] Philippe Dubois, Olivier Coulembier, Jean-Marie Raquez, Wiley-VCH Verlagsgesellschaft, 2009, 1, 287-306 p.Chapter in book (Other academic)
  • 19.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Källrot, Martina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    POLY 585-Covalent surface modification of degradable polymers2007In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 234Article in journal (Other academic)
  • 20.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Controlled synthesis of star-shaped homo- and co-polymers of aliphatic polyesters2006In: 7th International Biorelated Polymers Symposium, 2006, 37-38 p.Conference paper (Refereed)
    Abstract [en]

    The challenges in finding a material with the proper characteristics for a given tissue engineering application are several. One solution is improving the ability to tailor the mechanical and physical properties along with the degradation profile of aliphatic polyesters, by for example alterations in their composition and architecture. In this study, well-defined star-shaped aliphatic polyesters constituted of four arms were synthesized. As a model system, L,L-lactide and a spirocyclic tin initiator was chosen and the affect of the solvent, temperature and monomer-to-initiator ratio on the number average molecular weight, the molecular weight distribution and the conversion of the polymers was shown. Consecutively, we proved that well-defined star-shaped block copolymers composed of 1,5-dioxepan-2-one and L,L-lactide with narrow molecular weight distributions and controlled block lengths can be synthesized using this system.

  • 21.
    Albertsson, Ann-Christine
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Olander, Björn
    KTH, Superseded Departments, Polymer Technology.
    Edlund, Ulrica
    KTH, Superseded Departments, Polymer Technology.
    Källrot, Martina
    KTH, Superseded Departments, Polymer Technology.
    Increased biocompatibility by surface modification2004In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 228, U508-U508 p.Article in journal (Other (popular science, discussion, etc.))
  • 22.
    Albertsson, Ann-Christine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Varma, Indra Kumari
    Centre for Polymer Science and Engineering, Indian Institute of Technology, Dehli, India.
    Lochab, Bimlesh
    Centre for Polymer Science and Engineering, Indian Institute of Technology, Dehli, India.
    Finne Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Kumar, Kamlesh
    Centre for Polymer Science and Engineering, Indian Institute of Technology, Dehli, India.
    Design and Syntesis of Different Types of Poly(Lactic acid)2010In: Poly(Lactic Acid): Synthesis, Structures, Properties, Processing and Applications / [ed] Rafael Auras, Loong-Tak Lim, Susan E. M. Selke, Hideto Tsuji, John Wiley & Sons, 2010, 43-58 p.Chapter in book (Other academic)
  • 23.
    Albán Reyes, Diana Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden .
    Svedberg, Anna
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sundman, Ola
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The influence of different parameters on the mercerisation of cellulose for viscose production2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 2, 1061-1072 p.Article in journal (Refereed)
    Abstract [en]

    A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

  • 24. Ali, Majid
    et al.
    Bashir, Tariq
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Optimization of oCVD Process for the Production of Conductive Fibers2011Conference paper (Other academic)
    Abstract [en]

    Electro active textile fibers are key components in smart and interactive textile applications. In our previous study, we produced poly(3,4-ethylenedioxythiophene) (PEDOT) coat edviscose fibers by using oxidative chemical vapordeposition (OCVD) technique. We tried FeCl3 as oxidant and found optimum reaction conditions at which better electrical as well as mechanical properties of conductive fibers could be achieved.

  • 25.
    Alin, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Migration from plastic food packaging during microwave heating2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Microwave heating of food has increased rapidly as a food processing technique. This increases the concern that chemicals could migrate from food packaging to food. The specific effect of microwave heating in contrast to conventional heating on overall and specific migration from common plastic food storage boxes was studied in this work. The purpose was especially to determine the interaction effects of different plastics in contact with different types of foods during microwave heating. The study focused on polycarbonate (PC), poly(ethylene terephthalate) (PET), polypropylene homo-polymer (PP), co-polymer (PP-C) and random co-polymer (PP-R) packages. The migration determinations were evaluated at controlled times and temperatures, using a MAE device. The migrants were analyzed by GC-MS and HPLC. ESI-MS was evaluated as a new tool for migration determinations. Food/food simulant absorption and changes in degree of crystallinity during heating were also followed.

    Significant degradation of antioxidants Irgafos 168 and Irganox 1010 in PP packages occurred during microwave heating of the packages in food simulants containing ethanol, resulting in the formation of antioxidant degradation products. Degradation of PC by Fries chain rearrangement reaction leading to formation of 9,9-dimethylxanthene, and transesterification of PET leading to formation of diethyl terephthalate, were also observed after microwave heating the packages in ethanol and 90/10 isooctane/ethanol. These reactions were not observed during conventional heating of the packages at the same temperature, or after microwave heating of the packages in liquid food (coconut milk). The microwave heating also significantly increased the migration of cyclic oligomers from PET into ethanol and isooctane at 80 °C. Migration of compounds into coconut milk was slightly lower than calculated amounts using the EU mathematical model to predict migration of additives into foodstuffs. The results thus show that the use of ethanol as a fat food simulant during microwave heating can lead to a significant overestimation of migration as well as degradation of polymer or the incorporated additives.

    Some other detected migrants were dimethylbenzaldehyde, 4-ethoxy-ethyl benzoate, benzophenone, m-tert-butyl phenol and 1-methylnaphthalene. All identified migrants with associated specific migration limit (SML) values migrated in significantly lower amounts than the SML values during 1 h of microwave heating at 80 °C. The antioxidant diffusion coefficients in PP and PP co-polymers showed larger relative differences than the corresponding degrees of crystallinity in the same polymers and PP-R showed by far the fastest migration of antioxidants.

  • 26.
    Alin, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Microwave heating effects on degradation and migration of additives from polypropylene packaging2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The effect of different food types, polymer qualities and microwaves on the overall and specific migration during microwave heating of plastic packaging was investigated to better understand the packaging-food interactions and the effect of microwaves on food packaging. This work focuses on the migration of chemical compounds to food simulants from commercially available polypropylene packages. Packages used were made of polypropylene homopolymer (PP), co-polymer (PP-C) and random co-polymer (PP-R). Polymers matrix changes were monitored by following possible changes in crystallinity after microwave heating. Antioxidants Irgafos 168 and Irganox 1010 were present in all the three PP packages. Other volatiles, primarily degradation products of antioxidants, were also detected and identified in the unaged packages. Significant antioxidant degradation took place during microwave heating of the packages in the fatty food simulants 90/10 isooctane/ethanol and ethanol resulting in the formation and migration of degradation products while no degradation of antioxidants was detected during conventional heating of the packages in the fatty food simulants. Antioxidant Irgafos 168 and Irganox 1010 migration rates were otherwise similar during microwave heating as during conventional heating to the fatty food simulants and antioxidant diffusion coefficients were similar to earlier established values obtained during conventional heating. Antioxidant migration rates from the three polymers to fatty food simulants differed largely with respect to PP type and increased with decreasing degree of crystallinity in the materials, PP-R showing the highest migration rate. Swelling in isooctane food simulant caused the antioxidant diffusion coefficients to increase by factors of 100-1000 at 80 ºC and decreased the temperature dependence of antioxidant migration. It also increased the overall migration to above established overall migration limits during both microwave and conventional heating. Electrospray ionization mass spectrometry (ESI-MS) was shown to be a valuable new tool for additive migration analysis of compounds not detectable by HPLC or GC-MS.

  • 27.
    Alin, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Type of Polypropylene Material Significantly Influences the Migration of Antioxidants from Polymer Packaging to Food Simulants During Microwave Heating2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 118, no 2, 1084-1093 p.Article in journal (Refereed)
    Abstract [en]

    Three different polypropylene materials, polypropylene homopolymer (PP), propylene-ethylene random copolymer (PP-R), and propylene-ethylene copolymer (PP-C) are commonly used in plastic containers designed for microwave heating of food. Migration of antioxidants, Irganox 1010 and Irgafos 168, from PP. PP-R, and PP-C during microwave heating in contact with different food simulants was investigated by utilizing microwave assisted extraction (MAE) and high performance liquid chromatography (HPLC). The polypropylene material significantly influenced the migration rate, which decreased in the order of increasing degree of crystallinity in the materials. PP homopolymer was the most migration resistant of the studied materials especially in contact with fatty food simulants. The use of isooctane as fatty food simulant resulted in rapid depletion of antioxidants, while migration to another fatty food simulant, 96% ethanol, was much more limited. Migration to aqueous and acidic food simulants was in most cases under the detection limits irrespective of microwaving time and temperature. The diffusion coefficients were similar to what have been found previously under similar conditions but without microwaves. The effect of swelling was shown by the large increase in the calculated diffusion coefficients when isooctane was used as food simulant instead of 96% ethanol. (C) 2010 Wiley Periodicals, Inc. I Appl Polym Sci 118: 1084-1093,2010

  • 28.
    Alin, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Microwave heating causes rapid degradation of antioxidants in polypropylene packaging leading to greatly increased specific migration to food simulants as shown by ESI-MS and GC-MS2011In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 59, no 10, 5418-5427 p.Article in journal (Refereed)
    Abstract [en]

    Microwave heating of commercial microwavable polypropylene packaging in contact with fatty food simulants caused significant antioxidant degradation and increased specific migration as shown by electrospray ionization-mass spectrometry (ESI-MS) and gas chromatography-mass spectrometry (GC-MS). Degradation of the antioxidants Irgafos 168 and Irganox 1010 was not detected during conventional heating of polypropylene packaging at the same temperature. The migration into aqueous food simulants was primarily restricted by the water solubility of the migrants. Using isooctane as fatty food simulant caused significant swelling and greatly enhanced overall migration values compared to the other fatty food simulant, 99.9% ethanol, or the aqueous food simulants 10% ethanol, 3% acetic acid, or water. ESI-MS spectra clearly reflected the overall migration values, and the number and amount of compounds detected decreased as the hydrophilicity of the food simulant increased. ESI-MS was shown to be an excellent tool for the analysis of semivolatile migrants and a good complement to GC-MS analysis of volatile migrants.

  • 29.
    Alin, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Migration from polycarbonate packaging to food simulants during microwave heating2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 8, 1387-1395 p.Article in journal (Refereed)
    Abstract [en]

    The interactions between polycarbonate (PC) packaging and different food simulants during microwave heating were evaluated by identifying the compounds migrating into aqueous, alcoholic and fatty food simulants. The migration of compounds, such as 9,9-dimethylxanthene and m-tert-butyl-phenol, from the PC package to ethanol and isooctane increased significantly during microwave heating as compared to conventional heating. The increase in migration can be explained by degradation caused by microwave heating and/or stronger food simulant interactions. Depending on the food simulant the migrants were quantified either by multiple headspace–solid-phase micro-extraction (MHS-SPME) or direct injection in combination with gas chromatography-mass spectrometry. A partial least squares (PLS) regression model was developed to predict the extraction efficiency for headspace–solid-phase micro-extraction (HS-SPME) of food package migrants from the analyte properties. The most significant property for prediction of the enrichment factors was the octanol-water partition coefficient (log Kow). Polydimethylsiloxane (PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibers were compared for the extraction of the migrants. High correlation was found between the PDMS and PDMS/DVB enrichment factors (R2=0.98), but the extraction by PDMS/DVB fiber was much more efficient compared to the extraction by PDMS fiber. The detection limits after SPME extraction by PDMS/DVB fiber were 1, 0.1 and 3 ng/L for 4-ethoxy-ethyl-benzoate, 2,4-di-tert-butyl-phenol and benzophenone, respectively.

  • 30.
    Alin, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Combined Chromatographic and Mass Spectrometric Toolbox for Fingerprinting Migration from PET Tray during Microwave Heating2013In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 61, no 6, 1405-1415 p.Article in journal (Refereed)
    Abstract [en]

    A combined chromatographic and mass spectrometric toolbox was utilized to determine the interactions between poly(ethylene terephthalate) (PET) food packaging and different food simulants during microwave heating. Overall and specific migration was determined by combining weight loss measurements with gas chromatography-mass spectrometry (GC-MS) and electrospray ionization mass spectrometry (ESI-MS). This allowed mapping of low molecular weight migrants in the molecular range up to 2000 g/mol. Microwave heating caused significantly faster migration of cyclic oligomers into ethanol and isooctane as compared to migration during conventional heating at the same temperature. This effect was more significant at lower temperature at which diffusion rates are generally lower. It was also shown that transesterification took place between PET and ethanol during microwave heating, leading to formation of diethyl terephthalate. The detected migrants included cyclic oligomers from dimer to hexamer, in most cases containing extra ethylene glycol units, and oxidized Irgafos 168. ESI-MS combined with CID MS-MS was an excellent tool for structural interpretation of the nonvolatile compounds migrating to the food simulants. The overall migration was below the overall migration limit of 10 mg/dm(2) set by the European commission after 4 h of microwave heating at 100 degrees C in all studied food simulants.

  • 31.
    Alipour, Nazanin
    KTH, School of Chemical Science and Engineering (CHE).
    Migration of different additives from polyethylen2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Insecticidal polymer nets are used to combat malaria. It combines polyethylene fibers and two chemicals, deltamethrin (DM) and a synergist piperonyl butoxide (PBO) which increases efficacy of deltamethrin. The migration and evaporation of DM and PBO through polyethylene was studied in this report. The crystallinity and melting temperature of pristine DM, a prepared polymer compound and Vestergaard samples were characterized by differential scanning calorimetry (DSC). It was found that DM does not crystallize and remains liquid after cooling to room temperature. A small depression in melting temperature of the polymer was observed when samples were covered by a layer of DM. Rate constants and activation energies of evaporation were determined by thermogravimetry (TG) including pristine DM, PBO and their solution and also PE compound and Vestergaard samples. Higher rate constant for DM and PBO solution was observed in comparison with pure DM and PBO. The migration of DM and PBO from the polyethylene was studied in liquid water and air with different relative humidity (60 and 80%) at 80 ⁰C. Water caused degradation of the DM present in the material and generated product species containing nitro and amine groups. Besides, the degraded products including some undegraded DM formed a layer on the surface of the material (blooming). Liquid chromatography (HPLC) and infrared spectroscopy (IR) showed faster migration of the active species in liquid water than in air with 60 and 80% RH; (approximately 7 times for DM and 2 times for PBO). Some DM agglomerates was observed on the plate surface after exposure to air with 80 % RH.

  • 32.
    Alipour, Nazanin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Yu, Shun
    Roth, Stephan
    Brüning, Karsten
    Vieyres, Arnaud
    Schneider, Konrad
    Structure and properties of polyethylene-based and EVOH-based multilayered films with layer thicknesses of 150 nm and greater2015In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 64, 36-51 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the structure and properties of two multilayered systems where polymers in adjacent layers were either miscible or immiscible. The miscible system consisted of 2, 17, 18, 24 and nominally 288 layers of alternating low-density (LDPE) and low-density/linear-low density (mPE) polyethylene layers with observed thicknesses ranging from 150 nm to 20 urn. The immiscible system consisted of 5 and 19 layer films with a combination of poly(ethylene-co-vinyl alcohol) (EVOH) (thickness: 9 and 1 gm, respectively), LDPE (17 and 7 gm) and a polyethylene adhesive (3 and 1 gm). The purpose of the multi-layering was to increase the crack growth resistance and, in the EVOH-based system, to decrease the oxygen transmission rate. Indeed, the crack growth resistance, as measured on tensile-tested notched films, increased with increasing number of layers. The thinnest polyethylene and polyethylene adhesive layers showed a clear ductile failure when fractured even in liquid nitrogen. Simultaneous synchrotron wide-angle/small-angle X-ray scattering and tensile testing indicated no new deformation features with changes in the layer thickness. The oxygen permeability was the same in the 5- and 19-layer EVOH-based films, but the uptake of n-hexane was strongly reduced in the 19-layer films, demonstrating the effective protective role of the EVOH layers. The n-hexane desorption data of the 2-layer LDPE/mPE film was successfully modeled using the diffusivities and solubilities of the single layers. Crystallization was slower and more confined in the films with thinner layers. The interlayer mixing in the melt (measured by isothermal crystallization from melts of initially layered polyethylene-based systems) was, as expected, significantly faster in the 24- and 288-multilayer films than in the 2-layer film.

  • 33. Amanizadeh, Farhad
    et al.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mobarakeh, Hamid Salehi
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Starve fed emulsion copolymerization of vinyl acetate and 1-hexene at ambient pressure2014In: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 63, no 10, 1850-1855 p.Article in journal (Refereed)
    Abstract [en]

    A novel emulsion copolymer of vinyl acetate (VAc) and 1-hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1-hexene in the copolymer chains and glass transition temperature (T-g) as well as on bulk properties like minimum film-formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non-polar 1-hexene monomers of low reactivity. The copolymer showed a lower T-g and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1-hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc-1-hexene films compared to PVAc films.

  • 34.
    Aminlashgari, Nina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    SALDI-MS Method Development for Analysis of Pharmaceuticals and Polymer Degradation Products2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) was evaluated as a new tool for analysis of polymer degradation products. A SALDI method was developed enabling rapid analysis of low molecular mass polyesters and their degradation products. In addition, the possibility to utilize nanocomposite films as easy-to-handle surfaces for analysis of pharmaceutical compounds was investigated.

    Poly(ε-caprolactone) was used as a model compound for SALDI-MS method development. The signal-to-noise values obtained by SALDI-MS were 20 times higher compared to traditional matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) of the same samples with 2,5-dihydroxybenzoic acid as a matrix. Halloysite nanoclay and magnesium oxide showed best potential as surfaces and clean backgrounds in the low mass range were observed. The SALDI-MS method for the analysis of polyester degradation products was also verified by electrospray ionization-mass spectrometry (ESI-MS). An advantage over ESI-MS is the possibility to directly analyze degradation products in buffer solutions. Compared to gas chromatography-mass spectrometry (GC-MS) it is possible to analyze polar compounds and larger molecular mass ranges at the same time as  complicated extraction steps are avoided.

    The possibility to use nanocomposite films as surfaces instead of free nanoparticles was evaluated by solution casting of poly(lactide) (PLA) films with eight inorganic nanoparticles. The S/N values of the pharmaceutical compounds, acebutolol, propranolol and carbamazepine, analyzed on the nanocomposite surfaces were higher than the values obtained on the surface of plain PLA showing that the nanoparticles participated in the ionization/desorption process even when they are immobilized. Beside the ease of handling, the risk for instrument contamination is reduced when nanocomposites are used instead of free nanoparticles. The signal intensities depended on the type of drug, type and concentration of nanoparticle. PLA with 10 % titanium oxide or 10 % silicon nitride functioned best as SALDI-MS surfaces.

  • 35.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Surface Assisted Laser Desorption Ionization-Mass Spectrometry (SALDI-MS) for Analysis of Polyester Degradation Products2012In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 23, no 6, 1071-1076 p.Article in journal (Refereed)
    Abstract [en]

    Novel surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) method was developed for rapid analysis of low molecular mass polyesters and their degradation products by laser desorption ionization-mass spectrometry. Three polycaprolactone materials were analyzed by the developed method before and after hydrolytic degradation. The signal-to-noise values obtained by SALDI-MS were 20-100 times higher compared with the ones obtained by using traditional MALDI-MS matrices. A clean background at low mass range and higher resolution was obtained by SALDI-MS. Different nanoparticle, cationizing agent, and solvent combinations were evaluated. Halloysite nanoclay and magnesium hydroxide showed the best potential as SALDI surfaces. The SALDI-MS spectrum of the polyester hydrolysis products was verified by ESI-MS. The developed SALDI-MS method possesses several advantages over existing methods for similar analyses.

  • 36.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Shariatgorji, Mohammadreza
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Ilag, Leopold L.
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry2011In: Analytical Methods, ISSN 1759-9660, Vol. 3, no 1, 192-197 p.Article in journal (Refereed)
    Abstract [en]

    The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.

  • 37.
    ANDERSSON, JOAKIM
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    ERIKSON, SOFIA
    KTH, School of Chemical Science and Engineering (CHE).
    HÖGLUND, MARTIN
    KTH, School of Chemical Science and Engineering (CHE).
    GÖTHE, VICTORIA
    KTH, School of Chemical Science and Engineering (CHE).
    Enzymkatalys av oligomerer från förnyelsebara resurser2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Naturen är en källa till en mängd komplexa molekyler som har potential att användas inom industrin. En del av dessa molekyler kan utvinnas från suberin som bland annat finns i träd och i särskilt hög grad i björknäver. Genom att lösa upp näver i natriumhydroxid kan suberin sönderdelas i mindre beståndsdelar vilka sedan kan extraheras.  En av dessa beståndsdelar är 9,10-epoxi-18-hydroxioktadekansyra (EFA), vilken har tre olika funktionella grupper: en epoxid-, en hydroxid- och en karboxylgrupp.  De tre omnämnda funktionella grupperna påvisar det breda potentiella användningsområdet för denna molekyl.  EFA skulle därmed kunna vara intressant att utnyttja i utvecklingen av nya, gröna material.

    Målet med detta projekt är att extrahera EFA från näver för att sedan via enzymkatalys syntetisera oligomerer med dimetyladipat (DA).

    Under projektet utfördes ett flertal extraktioner med varierande resultat vilket visar på metodens känslighet. Troligen har pH samt den använda näverns individuella egenskaper stor inverkan på extraktionen och dess utbyte. Den fjärde extraktionen gav 0,44 g EFA vilket innebar ett utbyte på 12%.

    EFA polymeriserades via enzymatisk katalys med CalB (Lipas B från Candida Antarctica) vilket gav en polymer som efter 1H-NMR-analys kunde konstateras ha en bibehållen epoxidgrupp. Genom att använda DA som ändgrupp och samtidigt reglera det stökiometriska förhållandet mellan reaktanterna, kunde polymerisationsgraden kontrolleras.  Genom MALDI-ToF-analys kunde det fastslås att det fanns en trend typisk för enzymkatalyserade polymerer i det erhållna spektrumet. Denna trend indikerade att monomeren EFA fanns kvar men även att en polymerisation ägt rum och oligomerer med polymerisationsgrader ett och två hade bildats.   

  • 38.
    Andersson, Richard
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Cabedo, L.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Superparamagnetic [sic] nanofibers by electrospinning2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 26, 21413-21422 p.Article in journal (Refereed)
    Abstract [en]

    The preparation of superparamagnetic thin fibers by electrospinning dispersions of nanosized magnetite (Fe3O4, SPIO/USPIO) in a PMMA/PEO polymer solution is reported. The saturation magnetization and coercivity were not affected by the concentration (0, 1, 10, 20 wt%) or fiber orientation, showing hysteresis loops with high magnetization (64 A m(2) kg(-1) @ 500 kA m(-1)) and record low coercivity (20 A m(-1)). AC susceptibility measurements vs. temperature at frequencies from 60 to 2 kHz confirmed superparamagnetism. The mechanical properties were only slightly dependent on the particle concentration because the nanoparticles were separately encapsulated by the polymer. A uniform fibre fracture cross section was found at all the investigated particle contents, which suggests a strong interaction at the polymer/particle interface. A theoretical value of the magnetic low field susceptibility was calculated from the Langevin function and compared with measured values. The results show a distinct but concentration-independent anisotropy, favoring magnetization along the fiber orientation with no sign of exchange interaction, explained by complete nanoparticle separation. Superparamagnetism cannot be inferred from particle size alone, so a relevant interpretation and criterion for superparamagnetism is presented, in accordance with Neel's original definition. From the measurements, it can be concluded that magnetic characterization can be used to elucidate the material morphology beyond the resolution of available microscopy techniques (TEM and SEM).

  • 39.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Structural properties and micromechanics of PMMA-based electrospun hybrid fibers2013Licentiate thesis, comprehensive summary (Other academic)
  • 40.
    Andronova, Natalia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bioresorbable copolymers with tailored properies: innovative materials för soft tissuel engineering2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The emerging need for new synthetic materials for soft tissue engineering applications encourages the search for innovative polymers having interesting properties. Ring-opening polymerization of lactones and lactides initiated by tin alkoxides has received particular attention due to the versatility of the method for building up well-defined biodegradable structures. The controlled reactions together with a careful choice of comonomers and copolymer composition make it possible to create materials with desired molecular architecture and properties.The aim of the work described in this thesis was to design aliphatic bioresorbable copolymers with new structures and controlled properties for potential application in soft tissue engineering. The first part of the work was focused on the surface properties of the materials synthesized for biomedical application. Solution-cast film triblock copolymers of L-lactide (LLA) and 1,5-dioxepan-2-one (DXO), subjected to thermal treatment have been studied. The effects of molecular weight, polymer composition, cooling rate, and casting solution concentration on the nanostructure surface morphology and topography have been investigated by atomic force microscopy (AFM). The surface characterization of the annealed triblock copolymers revealed well-defined fiber features formed as a result of a melt-induced micro-phase separation during crystallization. The dimensions and shape of the formations could be related to the copolymer composition and annealing conditions, and this makes it possible to create controlled and well-defined surface structure. The results of cell adhesion studies on annealed triblock copolymers indicate that these materials favor fibroblast growth and spreading, which makes them promising candidates for applications as bioresorbable membranes.In the next stage of the work, linear and network copolymers of ε-caprolactone (CL) and DXO with a controlled composition and controlled hydrophilicity have been synthesized. The molar fraction of DXO in the copolymers affected their mechanical, thermal and surface properties. The hydrophilicity was tailored by changing the monomer composition in the copolymers. The AFM measurements on the linear copolymers showed that short fibrillar structures were formed upon crystallization from the melt. The supple CL-DXO networks were easy to cast and could easily be removed from the mould surface, so that it is possible to use this material for embossing procedures without the risk of damaging the surface pattern during removal from the mould.

  • 41.
    Andronova, Natalia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Srivastava, Rajiv
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone2005In: Polymer journal, ISSN 0032-3896, Vol. 46, no 18, 6746-6755 p.Article in journal (Refereed)
    Abstract [en]

    The synthesis and characterization of degradable polymeric networks for biomedical applications was performed. Cross-linked films of poly(epsilon-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) having various mole fractions of monomers and different cross-link densities were successfully prepared using 2,2'-bis-(epsilon-caprolactone-4-yl) propane (BCP) as cross-linking agent. Reaction parameters were carefully examined to optimise, the film-formin.,, conditions. Networks obtained were elastomeric materials. easy to cast and remove from the mould. Effect of CL content and cross-link density on the final properties of the polymer network was evaluated. High CL content or degree of cross-linking led to increase in Young's modulus and decrease in elongation at break. An increase in crystalline domains in films having a higher CL content was observed by optical microscopy. A greater thermal stability was observed in films having a high CL content. The hydrophilicity of the materials could be tailored by changing the CL content. The surface of the films became rougher with higher CL content.

  • 42.
    Antoni, Per
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Functional Dendritic Materials using Click Chemistry: Synthesis, Characterizations and Applications2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The need for new improved materials in cutting edge applications is constantly inspiring researchers to developing novel advanced macromolecular structures. A research area within advanced and complex macromolecular structures is dendrimers and their synthesis. Dendrimers consist of highly dense and branched structures that have promising properties suitable for biomedical and electrical applications and as templating materials. Dendrimers provide full control over the structure and property relationship since they are synthesized with unprecedented control over each reaction step. In this doctoral thesis, new methodologies for dendrimer synthesis are based on the concept of click chemistry in combination with traditional chemical reactions for dendrimer synthesis.

    This thesis discusses an accelerated growth approach, dendrimers with internal functionality, concurrent reactions and their applications.

    An accelerated growth approach for dendrimers was developed based on AB2- and CD2-monomers. These allow dendritic growth without the use of activation or deprotection of the peripheral end-groups. This was achieved by combining the chemoselective nature of click chemistry and traditional acid chloride reactions.

    Dendrimers with internal azide/alkyne functionality were prepared by adding AB2C monomers to a multifunctional core. Dendritic growth was obtained by employing carbodiimide mediated chemistry. The monomers carry a pendant C-functionality (alkyne or azide) that remains available in the dendritic interior resulting in dendrimers with internal and peripheral functionalities.

    The orthogonal nature of click chemistry was utilized for the simultaneous assembly of monomers into dendritic structures. Traditional anhydride chemistry and click chemistry were carried out concurrently to obtain dendritic structures. This procedure allows synthesis of dendritic structures using fewer purification steps.

    Thermal analyses on selected dendrimers were carried out to verify their use as templates for the formation of honeycomb membranes. Additionally, a light emitting dendrimer was prepared by coupling of azide functional dendrons to an alkyne functional cyclen core. A Europium ion was incorporated into the dendrimer core, and photophysical measurements on the metal containing dendrimer revealed that the formed triazole linkage possesses a sensitizing effect.

  • 43.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Structural Modifications of Lignosulphonates2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lignosulphonates are by‐products from the sulphite pulping process for the manufacture ofspecialty dissolving pulps and paper. During the liberation of the cellulose, the lignin isfractionated and solubilised through covalent addition of sulphonic acid groups at variouspositions in the structure. The formed sulphonated lignin, lignosulphonate is then furtherisolated and refined.

    The amphiphilic nature of lignosulphonates has enabled them to be used as additives to varioussuspensions to improve their dispersion and stability. The by far largest utilisation oflignosulphonates is as dispersants in concrete. Here, lignosulphonates act by dispersing cementparticles to prevent flocculation, un‐even particle distribution and reduced strengthdevelopment. The dispersion is achieved through steric and electrostatic repulsion of the cementparticles by the lignosulphonate polymer. This behaviour is intimately linked with the overallsize and amount of charged groups in the dispersing polymer. Traditional modifications oflignosulphonates have been limited to removal of sugars, filtration and fractionation. Thesemodifications are not sufficient for utilisation of lignosulphonates in high‐strength concrete. Heresynthetic dispersants and superplasticisers are used which are considerably more efficient evenat low dosages. To compete with these, additional modifications of lignosulphonates are likely tobe necessary. The molecular weight and functional group composition have been identified anddescribed as the most interesting parameters that can be modified.

    Currently, no suitable method exists to increase the molecular weight of lignosulphonates.Oxidation by the natural radical initiating enzyme laccase is an interesting tool to achieve suchmodifications. In this thesis several aspects of the mechanism through which this enzyme reactswith lignin and lignosulphonate structures have been elucidated through model compoundstudies. Further studies showed that laccase alone was a highly efficient tool for increasing themolecular weight of commercial lignosulphonates at low dosages and in short incubation times.Immobilisation of the laccase to a solid support to enable re‐utilisation was also investigated.

    Modification of functional group composition of lignosulphonates was achieved throughozonolysis and the Fenton’s reagent, a mixture of hydrogen peroxide and iron(II)acetate.Introduction of charged carboxylic groups was achieved through opening of the benzyl rings oflignosulphonates. It was found that a two‐stage process consisting of laccase oxidation followedby ozonolysis was an efficient technique to create a polymer enriched with carboxylic acidgroups with a sufficient molecular size.

    Oxidation by the Fenton’s reagent was shown to yield similar modifications as the combinedlaccase/ozonolysis treatment albeit with less pronounced results but with a large level of controlthrough variation of a number of reaction parameters. The Fenton’s reagent can therefore be aninteresting alternative to the aforementioned two‐stage treatment.

    These modifications are interesting for large‐scale applications not only because of theirsimplicity in terms of reaction parameters but also because of the ubiquity of the used enzymeand the chemicals in the pulp and paper industry.

  • 44.
    Areskogh, Dimitri
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Investigation of the Molecular Weight Increase of Commercial Lignosulfonates by Laccase Catalysis2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 4, 904-910 p.Article in journal (Refereed)
    Abstract [en]

    Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.

  • 45.
    Arias Goa, Veluska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Macrostructural Design of Polylactide-based Materials for Improved Mechanical and Degradation Properties2014Licentiate thesis, comprehensive summary (Other academic)
  • 46.
    Arias, Veluska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Towards a retro-structural design of degradable aliphatic polyester-based materials2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increasing amount of accumulated plastic waste has led to a continuous search for degradable materials for use in a variety of applications. This eco-friendly approach contemplates the use of degradable alternatives to the inert polymers (the main components in plastics) used today and further engineering of their degradation pathways. The most extensively investigated group of degradable polymers is the poly(α-esters), due to their tailorable thermo-mechanical properties and degradability. However, degradation of these polymers can be undesirable or desirable depending on the time of occurrence. Thus, by controlling the degradation process, it is possible to predict and, consequently, tailor the materials’ lifetime for specific needs.Herein, a methodology to allow for a retro-structural design of degradable materials based on aliphatic polyesters is presented. Insights into the degradation behavior of the systems were obtained and further translated to different levels of structural designs to achieve desired macroscopic properties in terms of performance and degradability. Several combinational strategies based on polymer morphology, polymer structure and block design, were developed. As a result, homopolymers and block copolymers with projected degradation for different instances were created. Apart from bulk modifications in the material, it was shown that it was possible to tailor degradation pathways by means of specific interactions between polymer pairs in block copolymers and also in polymer blends. Furthermore, well-defined structure-property relationships are crucial when designing materials with specific degradability properties. In light of this, degradable polyester-based particles with tunable crystalline structures and, hence, physical properties, were developed. These particles proved to function as reinforcing agents in the creation of “green” homocomposites. These composites are promising alternatives in the search for materials that are completely degradable and sustainable.

  • 47.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Tuning the Degradation Profiles of Poly(L-lactide)-Based Materials through Miscibility2014In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 1, 391-402 p.Article in journal (Refereed)
    Abstract [en]

    The effective use of biodegradable polymers relies on the ability to control the onset of and time needed for degradation. Preferably, the material properties should be retained throughout the intended time frame, and the material should degrade in a rapid and controlled manner afterward. The degradation profiles of polyester materials were controlled through their miscibility. Systems composed of PLLA blended with poly[(R,S)-3-hydroxybutyrate] (a-PHB) and polypropylene adipate (PPA) with various molar masses were prepared through extrusion. Three different systems were used: miscible (PLLA/a-PHB5 and PLLA/a-PHB20), partially miscible (PLLA/PPA5/comp and PLLA/PPA20/comp), and immiscible (PLLA/PPA5 and PLLA/PPA20) blends. These blends and their respective homopolymers were hydrolytically degraded in water at 37 degrees C for up to I year. The blends exhibited entirely different degradation profiles but showed no diversity between the total degradation times of the materials. PLLA presented a two-stage degradation profile with a rapid decrease in molar mass during the early stages of degradation, similar to the profile of PLLA/a-PHB5. PLLA/a-PHB20 presented a single, constant linear degradation profile. PLLA/PPA5 and PLLA/PPA20 showed completely opposing degradation profiles relative to PLLA, exhibiting a slow initial phase and a rapid decrease after a prolonged degradation time. PLLA/PPA5/comp and PLLA/PPA20/comp had degradation profiles between those of the miscible and the immiscible blends. The molar masses of the materials were approximately the same after 1 year of degradation despite their different profiles. The blend composition and topographical images captured at the last degradation time point demonstrate that the blending component was not leached out during the period of study. The hydrolytic stability of degradable polyester materials can be tailored to obtain different and predetermined degradation profiles for future applications.

  • 48.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Olsén, Peter
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Selective degradation in aliphatic block copolyesters by controlling the heterogeneity of the amorphous phase2015In: Polymer Chemistry, ISSN 1759-9954, Vol. 6, no 17, 3271-3282 p.Article in journal (Refereed)
    Abstract [en]

    Controlling the course of the degradation of aliphatic polyesters is a key question when designing new degradable materials. It is shown herein that it is possible to predetermine the degradation path of aliphatic block copolyesters by controlling the heterogeneity of the amorphous phase, which in turn regulates the availability of the hydrolyzable groups in the polyester backbone. To demonstrate these processes, we synthesized a set of degradable materials based on poly(l-lactide) (PLLA), poly(ε-decalactone) (PεDL) and poly(ε-caprolactone) (PCL) with varying compositions. The materials were subjected to hydrolysis for a six months period. The materials composed of PLLA and PεDL exhibited a heterogeneous amorphous phase, whereas the materials composed of PCL and PεDL presented a more homogeneous phase. The kinetics of the degradation indicated that the slowest degradation rate was observed for the more homogeneous compositions. The degradation path of the heterogeneous amorphous phase materials was driven by a random chain scission process, whereas the more homogeneous composition presented a degradation path driven by a more selective chain scission. The confinement of the amorphous phase by the more hydrolytically stable PεDL permitted a selective degradation of the available hydrolyzable groups. The random and more selective chain scission processes were further verified by using previously determined molecular modeling based on Monte Carlo procedures. Topographical images and thermal analyses of the materials under different degradation periods correlated with the proposed degradation paths. Detailed insights and the ability to predetermine the degradation pathways of aliphatic polyesters will continue to expand the great potential of renewable materials and their use in specific applications for a future sustainable society.

  • 49.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Olsén, Peter
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Forecasting linear aliphatic copolyester degradation through modular block design2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 130, 58-67 p.Article in journal (Refereed)
    Abstract [en]

    The development of efficient methods to predict the degradation of renewable polymeric materials is continuously sought in the field of polymer science. Herein, we present a modular build-up approach to create polyester-based materials with forecasted degradation rates based on the hydrolysis of the constituent polymer blocks. This involved the strategic combination of critical factors affecting polyester hydrolysis, i.e. hydrophobicity and degree of crystallinity. The starting point of this method was a toolbox of polymers with different hydrophobicities and degrees of crystallinity, as well as an understanding of their inherent differences in hydrolysis rate. Knowledge of the hydrolysis of each polymer block module enabled the prediction of the overall degradation behavior of the constructed copolymers. Taking advantage of the primary factors that affect polymer degradation, block copolymers could be independently designed to incorporate soft or rigid and faster or slower degradation properties. This approach generated a shift for how molecular design can be used to predict the degradation behavior of intended materials for different applications.

  • 50.
    Aronsson, Christopher
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Zinc-Triggered Hierarchical Self-Assembly of Fibrous Helix-Loop-Helix Peptide Superstructures for Controlled Encapsulation and Release2016In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 49, no 18, 6997-7003 p.Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel route for hierarchical self-assembly of sub-micrometer-sized peptide superstructures that respond to subtle changes in Zn2+ concentration. The self-assembly process is triggered by a specific folding-dependent coordination of Zn2+ by a de novo designed nonlinear helix-loop-helix peptide, resulting in a propagating fiber formation and formation of spherical superstructures. The superstructures further form larger assemblies that can be completely disassembled upon removal of Zn2+ or degradation of the nonlinear peptide. This flexible and reversible assembly strategy of the superstructures enables facile encapsulation of nanoparticles and drugs that can be released by means of different stimuli.

    The full text will be freely available from 2017-09-15 16:25
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