MOLECULAR-STRUCTURES IN BIOPOLYMERS SOLS AND GELS

The short range molecular structure of agarose in the sol state and kappa-carrageenans in the gel state have been investigated by small-angle neutron scattering (0.1< q(nm-1) < 2.5). Agarose in the sol state possesses a rod-like conformation (minimum persistence length of 14 nm) with a mass per unit length consistent with a single helix. The existence of a double helix in the gel state is accordingly questioned. Agarose in sols from DMSO/WATER blends still exhibits the same rigidity yet the mass per unit length varies with solvent composition. It is surmised that this arises from strong complexation of agarose by DMSO which has consequences on the gelation propensity. Results obtained with kappa-carrageenans gels are accounted for by an array of rigid rods consisting of two populations of differing cross-sectional radius.