Calculation of viscometric constants, hydrodynamic volume, polymer–solvent interaction parameter, and expansion factor for three polysaccharides with different chain conformations

Abstract

The viscometric constants, K and a, for three polysaccharides: hydroxyethylcellulose (HEC); hydroxypropylcellulose (HPC); and chitosan, were calculated at 30 °C using intrinsic viscosity, [ η] and molecular weight ( M n, M w, M z) data. The polydispersity correction factor, q MHS, and hydrodynamic volume for each polymer sample were also calculated. The value of q MHS for the polymer samples was taken into account in the calculation of the viscometric constants. The polymer–solvent interaction parameters for the three polysaccharides were estimated by both semiempirical and numerical methods using intrinsic viscosity and molecular weight data. Hydrodynamic expansion factors were also estimated using the latter data. The quality of the solvents for the three polymers was compared using exponent a, polymer–solvent interaction parameter, and expansion factor data. This study resulted in the following constants for: (1) HEC with weight-average-molecular weight range, M w (36–511 kDa) in 0.05 mol L −1 NaNO 3 ( a = 0.600; K = 3.516 × 10 −3). (2) HPC with M w range (12–56 kDa) in (0.05 mol L −1 Na 2SO 4; pH 7.0) ( a = 1.080; K = 1.404 × 10 −5). (3) chitosan with M w range (141–327 kDa) in 0.83 mol L −1 CH 3COOH/0.3 mol L −1 NaCl ( a = 0.885; K = 1.464 × 10 −4). The values of 0.60, 1.08, and 0.885 for exponents a indicate that HEC, HPC, and chitosan behave as a flexible random coil, linear and extended conformations, respectively. The values of exponents a for the three polysaccharides appear to be inversely related to their K values. The results of the expansion factor were consistent with the results of exponent a and polymer–solvent interaction parameters.