EFFECT OF DEGREE OF DEACETYLATION OF CHITIN ON THE PROPERTIES OF CHITIN CRYSTALLITES

In the present article, chitin from crab shell was systematically deac etylated using a NaOH treatment with control of the reaction time. The degree of deacetylation, monitored using solid-state NMR, revealed th at the reaction was pseudo-first order. Based on this, swollen and NaO H-saturated particles are proposed as the reaction system. The weight loss of the partially saponified and neutralized samples after HCl hyd rolysis increased linearly with the degree of deacetylation. The cryst allinity of the samples was found to increase after acid hydrolysis. A ccording to conductimetric titration, the surface charge density of th e crystallites, after acid hydrolysis, was found to increase with base treatment time. The effect of surface charge on the formation of a ch iral nematic phase, due to the rodlike nature of the crystallites, was explored. These results show that because the contribution of charged particles to the ionic strength was significant the double layer comp ression was affected, especially since the surface charge density was close to the Manning limit. (C) 1997 John Wiley & Sons, Inc.