Studies on chitin and chitosan

Gummow, B.D., 1984. Studies on chitin and chitosan. PhD, Nottingham Trent University.

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Abstract

High molecular weight chitosan having a very low residual N-acetyl content has been produced by dissolution and reprecipitation of partially deacetylated chitin, followed by a further alkaline treatment Attempts-to carry out this second deacetylation step in solution using enzymes having amidase activity were unsuccessful, hydrolysis of the polymer chain occurring without any noticeable decrease in the N-acetyl content.

The uptake of Cu(II) ions from solution by chitosan films has been followed by-spectrophotometry after treatment of the films with metal complexing reagents. The equilibrium uptake was found to be inversely dependent upon film thickness, indicating that there is a concentration gradient within the films. When Cu(II) ions complexed with a tridentate ligand were used, interaction occurred with all the amine groups.

The ability of solutions of chitosan to induce metachromasy in anionic dyes has been studied. Reversal of metachromasy by addition of neutral electrolyte, urea, and ethanol, and by increase in temperature, was found to be similar to that reported for anionic polyelectrolyte/ cationic dye systems. The stoichiometry of the reaction between cationic groups on the polymer chain and anionic groups on the dye ions has been shown to be 1:1, and metachromatic titration techniques for determining the degree of N-acetylation of chitosan or measuring its concentration in solution, have been developed. The metachromatic behavior of a considerable number of dyes has been studied and the results show that the metachromatic shift may be either hypsochromic or bathochromic, and that there is no requirement for the charge on the dye ion to be delocalised. A new theory of metachromasy that does not invoke specific dye/site interaction is proposed and two experiments designed to test it: the dependence of the ease of reversal of metachromasy on the molecular weight of the polyelectrolyte and the stoichiometry of the interaction between chitosan and dibasic dyes. The results obtained, which cannot be explained in terms of current theory, support the new theory proposed here.

Item Type:	Thesis
Creators:	Gummow, B.D.
Date:	1984
ISBN:	9781369325690
Identifiers:	Number Type PQ10290320 Other
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Ward
Date Added:	08 Jul 2021 08:31
Last Modified:	10 Apr 2024 15:51
URI:	https://irep.ntu.ac.uk/id/eprint/43365

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