Dilute solution properties of carboxymethylchitins in high ionic-strength solvent

Abstract

The hydrodynamic characteristics in aqueous solution at ionic strength I=0.2 m of carboxymethylchitins of different degrees of chemical substitution have been determined. Experimental values varied over the following ranges: the translational diffusion coefficient (at 25.0°C), 1.1<10 7× D<2.9 cm 2 s −1; the sedimentation coefficient, 2.4< s<5.0 S; the Gralen coefficient (sedimentation concentration-dependence parameter), 130< k s<680 mL g −1; the intrinsic viscosity, 130<[ η]<550 mL g −1. Combination of s with D using the Svedberg equation yielded `sedimentation–diffusion' molecular weights in the range 40 000< M<240 000 g mol −1. The corresponding Mark–Houwink–Kuhn–Sakurada (MHKS) relationships between the molecular weight and s, D and [ η] were: [ η]=5.58×10 −3 M 0.94; D=1.87×10 −4 M −0.60; s=4.10×10 −15 M 0.39. The equilibrium rigidity and hydrodynamic diameter of the carboxymethylchitin polymer chain is also investigated on the basis of wormlike coil theory without excluded volume effects. The significance of the Gralen k s values for these substances is discussed.