Structure-property relationships in chitosan and selected film-forming derivatives

Dauth, R., 2002. Structure-property relationships in chitosan and selected film-forming derivatives. PhD, Nottingham Trent University.

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Converting chitosan into a recently patented polyanion in a confirmed non-degradative process constituted an improved method for determining molecular weight of chitosan by SEC-MALLS, previous problems with the polycation adsorbing onto columns with resulting inaccurate molecular weights being eliminated. From these reliable molecular weights the degree of polymerisation for the novel polymer and hence for chitosan were calculated and improved Mark-Houwink relationships for both polymers in a range of fraction of N-acetylation (FA) of 0.148 to 0.609 were established. The limiting viscosity number values, a parameter relationships and Huggins constants, when regarded as functions of Fa, are indices for conformational changes of the copolymer continua. For chitosan three stages were found, from an electrostatically controlled extended coil at constant and fairly high flexibility in the Fa range of approximately 0.0 to 0.25 to an progressively stiffening more rod-shaped conformation up to about 0.5, beyond which the stiffness again decreases together with the hydrodynamic volume. For the anionic derivative an overall inverse relationship of hydrodynamic volume and Fa could be established. Its shape bears rod-like characteristics at low Fa changing to increasingly random coil.

Different routes of preparing water/pH resistant chitosan-based membranes involved either hydrophobic substitution to increase organo-solubility in simple solvents like acetone or crosslinking with the environment- and bio-friendly crosslinking reagent citric acid. Promising results were obtained from both methods in the form of a novel organo-soluble chitosan derivative and a crosslinked product of chitosan with favourable acid resistance.

The scope of dye interaction for absolute compositional analysis was extended to complex systems of linear substitution as well as estimation of degree of crosslinking. The efficiency of N-acetylation was improved and a method for predicting anhydride amounts required for producing defined reacetylated material was established. The stability of chitin gels was influenced by FA, molecular weight and co-solvent proportions. The so far unpublished structurally strongly chitin-related N-carbamylchitosan exhibited similar solubility but different gelation behaviour.

Item Type: Thesis
Creators: Dauth, R.
Date: 2002
ISBN: 9781369323061
Divisions: Schools > School of Art and Design
Record created by: Linda Sullivan
Date Added: 30 Nov 2020 16:20
Last Modified: 21 Sep 2023 09:39

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