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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 4, Number 2
February 20, 1983 

Acid-Base Equilibria and Related Properties of Chitosan
Joon Woo Park, Kyung-Hee Choi, Kwanghee Koh Park
The pKa of -NH3+ group of chitosan in water was 6.2, while that of D-glucosamine-HCl, monomer of chitosan, was found to be 7.8. The difference of pKa values between chitosan and D-glucosamine was attributed to the strong electrostatic interaction between -NH3+ groups in chitosan. The apparent binding constant of Cu2+ to D-glucosamine was estimated to be 1×104. For chitosan, no significant binding of Cu2+ to the polymer was observed when pH < 5, but strong cooperative binding was observed near pH 5.1. The mechanism of such cooperativity was proposcd. Chitosan in solution exhibited typical polyelectrolytic behaviors: viscosity increases with increased amount of charged group, and decreases with addition of salt. The concentration dependence of viscosity was measured, and the Huggins parameters and intrinsic viscosity were calculated at various ionic strength. The results were interpreted in terms of molecular properties of the chitosan molecule.
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