Intrinsic viscosity-molecular weight relationship for chitosan

The intrinsic viscosity-molecular weight relationship for chitosan was dete rmined in 0.25 M acetic acid/0.25M sodium acetate. Chitosan samples with a degree of acetylation (Db) between 20 and 26% were prepared from shrimp-she ll chitosan by acid hydrolysis (HCl) and oxidative fragmentation (NaNO2). A bsolute molecular weights were measured by light scattering and membrane os mometry. Size exclusion chromatography (SEC) was used to determine average molecular weights (M-n, M-v, and M-w) and polydispersity. The following Mar k-Houwink-Sakurada equation (MHS) is proposed for chitosan of M-w in the ra nge of 35-2220 kDa: [eta] = 1.57 X 10(-4) M-v(0.79) = 1.57 X 10(-4) q(MHS)M(w)(0.79) = 1.49 X 1 0(-4) M-w(0.79). The value of the MHS exponent a suggests that chitosan behaves as a flexibl e chain in this solvent. Examination of MHS constants obtained in this work and those available in the literature with other solvents indicates that a and K are inversely related and that they are influenced by DA, and pH and ionic strength of the solvent. (C) 2000 John Wiley & Sons, Inc.