Master curve for concentration dependence of semi-dilute solution viscosity of chitosan homologues: the Martin equation

The concentration dependence of solution viscosity of polymers is described by Martin equation up to moderate concentrations, and the equation constan t provides a measure of polymer-polymer interactions in a given solvent. A set of chitosan homologues with degree of acetylation (DA) in the range of 17-25 % and intrinsic viscosity, [eta], in the range of 10.9-6.25 dlg(-1) w ere prepared by hydrolysis with HCl. Another set of chitosan fragments (DA of 22-26% and [eta] of 1.21-8.37 dlg(-1)) were prepared by oxidative scissi on with NaNO2. For the first set of chitosan homologues, the Martin constan t, was found to be 37.8x 10(-2) in 0.25 M HAc/0.25 M NaAc, while for the se cond set of homologues in 0.1 M HAc/0.02 M NaCl, it was 15.0x 10(-2). This suggests that the later was a better solvent for chitosan. A linear master curve in the dilute and semi-dilute regimes (c[eta] of 1.0 to 9.0) was obta ined to describe the concentration dependence of the flow behavior of chito san. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.