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Chitin nanofibers, networks and composites: Preparation, structure and mechanical properties
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Chitin is an important reinforcing component in load-bearing structures in many organisms such as insects and crustaceans (i.e. shrimps, lobsters, crabs etc.). It is of increasing interest for use in packaging materials as well as in biomedical applications. Furthermore, biological materials may inspire the development of new man-made material concepts. Chitinmolecules are crystallized in extended chain conformations to form nanoscale fibrils of about 3 nm in diameter. In the present study, novel materialshave been developed based on a new type of chitin nanofibers prepared from the lobster exoskeleton. Improved understanding about effects of chitin from crustaceans and chitin material preparation on structure is provided through Atomic Force Microscopy(AFM) (paper I&II), Scanning Transmission Electron Microscopy(STEM) (paper I&II), X-Ray Diffraction (XRD), Intrinsic Viscosity, solid state 13C Nuclear Magnetic Resonance (NMR) (paper II), Field Emission Scanning Electron Microscopy(FE-SEM) (paper I, II, III, IV & V), Ultraviolet-Visible Spectrophotometryand Dynamic Light Scattering (DLS) (paper III). The presence of protein was confirmed through colorimetric method(paper I & II). An interesting result from the thesis is the new features of chitin nanofiber including small diameter, high molar mass or nanofiber length,and high purity. The structure and composition of the nanofibers confirms this (paper I & II). Furthermore, the structure and properties of the corresponding materials confirm the uniqueness of the present nanofibers: chitin membrane (I & II), polymer matrix composites (III),and hydrogels (paper IV).

Improved mechanical properties compared with typical data from the literature were confirmed for chitin nanofiber membranes in paper II, chitin-chitosan polymer matrix composites in paper III, and chitin hydrogel in paper IV. Mechanical tests included dynamic mechanical analysis and uniaxial tensile tests. Mechanical properties of chitin hydrogels were evaluated based onrheological and compression properties (paper IV). The values were the highest reported for this kind of chitin material. Furthermore, the relationships between materials structure and properties were analyzed. For membranes and polymer matrix nanocomposites, the degree of dispersion is an important parameter. For the hydrogels, the preparation procedure is very simple and has interesting practical potential.

Chitin-binding characteristics of cuticular proteins areinteresting fornovel bio-inspired material development. In the present work(paper V), chitin nanofibers with newfeaturesincluding high surface area and low protein content were combined with resilin-like protein possessing the chitin-binding characteristics. Hydrated chitin-resilin nanocomposites with similar composition as in rubber-like insect cuticles were prepared. The main objective was to improve understanding on the role of chitin-binding domain on mechanical properties. Resilin is a rubber-like protein present in insects. The exon I (comprising 18 N-terminal elastic repeat units) together with or without the exon II (a typical cuticular chitin-binding domain) from the resilin gene CG15920 found in Drosophila melanogasterwere cloned and the encoded proteins were expressed as soluble products in Escherichia coli.Resilin-like protein with chitin-binding domain (designated as ResChBD) adsorbedin significant amount to chitin nanofiber surface andprotein-bound cuticle-like soft nanocomposites were formed. Although chitin bindingwas taking place only in proteinswith chitin-binding domain, the global mechanical behavior of the hydrated chitin-resilin nanocomposites was not so sensitive to this chitin-resilin interaction.

In summary, chitin is an interesting material component with high potential as mechanical reinforcement in a variety of nanomaterials. The present study reports the genesisof novel chitin nanofibers and outlines the basic relationships between structure and properties for materials based on chitin. Future work should be directed towards both bio-inspired studies of the nanocomposite chitin structures in organisms, as well as the industrial applications of chitin waste from the food industry. Chitin nanofibers can strengthen the properties of materials, andprovide optical transparency as well as biological activities such as antimicrobial properties.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , ix, 66 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:43
Keyword [en]
Chitin, chitin materials, membranes, hydrogels, nanocomposites, mechanical properties, bioinspiration, lobster
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-155528ISBN: 978-91-7595-312-0 (print)OAI: oai:DiVA.org:kth-155528DiVA: diva2:761483
Public defence
2014-11-28, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Formas, 63619
Note

QC 20141110

Available from: 2014-11-10 Created: 2014-11-06 Last updated: 2014-11-10Bibliographically approved
List of papers
1. Nanopaper membranes from chitin-protein composite nanofibers: Structure and mechanical properties
Open this publication in new window or tab >>Nanopaper membranes from chitin-protein composite nanofibers: Structure and mechanical properties
2014 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 7, 40121- p.Article in journal (Refereed) Published
Abstract [en]

Chitin nanofibers may be of interest as a component for nanocomposites. Composite nanofibers are therefore isolated from crab shells in order to characterize structure and analyze property potential. The mechanical properties of the porous nanopaper structures are much superior to regenerated chitin membranes. The nanofiber filtration-processing route is much more environmentally friendly than for regenerated chitin. Minerals and extractives are removed using HCl and ethanol, respectively, followed by mild NaOH treatment and mechanical homogenization to maintain chitin-protein structure in the nanofibers produced. Atomic force microscope (AFM) and scanning transmission electron microscope (STEM) reveal the structure of chitin-protein composite nanofibers. The presence of protein is confirmed by colorimetric method. Porous nanopaper membranes are prepared by simple filtration in such a way that different nanofiber volume fractions are obtained: 43%, 52%, 68%, and 78%. Moisture sorption isotherms, structural properties, and mechanical properties of membranes are measured and analyzed. The current material is environmentally friendly, the techniques employed for both individualization and membrane preparation are simple and green, and the results are of interest for development of nanomaterials and biocomposites.

Keyword
biomaterials, fibers, mechanical properties, membranes, porous materials
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-142316 (URN)10.1002/app.40121 (DOI)000331004100054 ()2-s2.0-84892586454 (Scopus ID)
Funder
Formas
Note

QC 20140305

Available from: 2014-03-05 Created: 2014-02-28 Last updated: 2017-12-05Bibliographically approved
2. Nanostructured hydrogel based on small diameter native chitin nanofibers: Preparation, structure and properties
Open this publication in new window or tab >>Nanostructured hydrogel based on small diameter native chitin nanofibers: Preparation, structure and properties
Show others...
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-155698 (URN)
Note

QS 2014

Available from: 2014-11-10 Created: 2014-11-10 Last updated: 2014-11-10Bibliographically approved
3. Nanostructured biocomposite films of high toughness based on native chitin nanofibers and chitosan
Open this publication in new window or tab >>Nanostructured biocomposite films of high toughness based on native chitin nanofibers and chitosan
2015 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 18, no 2, 99Article in journal (Refereed) Published
Abstract [en]

Chitosan is widely used in films for packaging applications. Chitosan reinforcement by stiff particles or fibers is usually obtained at the expense of lowered ductility and toughness. Here, chitosan film reinforcement by a new type of native chitin nanofibers is reported. Films are prepared by casting from colloidal suspensions of chitin in dissolved chitosan. The nanocomposite films are chitin nanofiber networks in chitosan matrix. Characterization is carried out by dynamic light scattering, quartz crystal microbalance, field emission scanning electron microscopy, tensile tests and dynamic mechanical analysis. The nanostructured biocomposite was produced in volume fractions of 0, 8, 22 and 56% chitin nanofibers. Favorable chitin-chitosan synergy for colloidal dispersion is demonstrated. Also, lowered moisture sorption is observed for the composites, probably due to the favorable chitin-chitosan interface. The highest toughness (area under stress-strain curve) was observed at 8 vol% chitin content. The toughening mechanisms and the need for well-dispersed chitin nanofibers is discussed. Finally, desired structural characteristics of ductile chitin biocomposites are discussed.

Keyword
Chitin nanofibers, Chitosan, Nanostructured, Nanocomposites, Mechanical Properties
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-155697 (URN)10.3389/fchem.2014.00099 (DOI)25478558 (PubMedID)2-s2.0-84987667407 (Scopus ID)
Note

Updated from E-publ to published. QC 20150630

Available from: 2014-11-10 Created: 2014-11-10 Last updated: 2017-12-05Bibliographically approved
4. Nanostructured membranes based on native chitin nanofibers prepared by mild process
Open this publication in new window or tab >>Nanostructured membranes based on native chitin nanofibers prepared by mild process
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2014 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, 255-263 p.Article in journal (Refereed) Published
Abstract [en]

Procedures for chitin nanofiber or nanocrystal extraction from Crustaceans modify the chitin structure significantly, through surface deacetylation, surface oxidation and/or molar mass degradation. Here, very mild conditions were used to disintegrate chitin fibril bundles and isolate low protein content individualized chitin nanofibers, and prepare nanostructured high-strength chitin membranes. Most of the strongly 'bound' protein was removed. The degree of acetylation, crystal structure as well as length and width of the native chitin microfibrils in the organism were successfully preserved. Atomic force microscopy and scanning transmission electron microscopy, showed chitin nanofibers with width between 3 and 4 nm. Chitin membranes were prepared by filtration of hydrocolloidal nanofiber suspensions. Mechanical and optical properties were measured. The highest data so far reported for nanostructured chitin membranes was obtained for ultimate tensile strength, strain to failure and work to fracture. Strong correlation was observed between low residual protein content and high tensile properties and the reasons for this are discussed.

Keyword
Preparation, Chitin nanofiber, Structure, Nanopaper membranes, Mechanical properties, Bound protein
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-153233 (URN)10.1016/j.carbpol.2014.05.038 (DOI)000341464600035 ()2-s2.0-84903189801 (Scopus ID)
Note

QC 20141016

Available from: 2014-10-16 Created: 2014-10-03 Last updated: 2017-12-05Bibliographically approved
5. Soft, bio-inspired chitin/protein nanocomposites: mechanical behavior and interface interactions between recombinant resilin-like proteins and chitin nanofibers
Open this publication in new window or tab >>Soft, bio-inspired chitin/protein nanocomposites: mechanical behavior and interface interactions between recombinant resilin-like proteins and chitin nanofibers
Show others...
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-155699 (URN)
Note

QS 2014

Available from: 2014-11-10 Created: 2014-11-10 Last updated: 2014-11-10Bibliographically approved

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