Novel high-performance materials from starch. 1. Factors influencing the lyotropic liquid crystallinity of some starch ethers

Starch ethers having side chains of various lengths, controlled and uniform degrees of substitution, and various amylose/amylopectin ratios were obtained by a one-step chemical modification of starch. Factors influencing the phase behavior of these starch ethers were carefully examined, and the ones having short side chains were found to exhibit lyotropic liquid crystallinity over wide ranges in degree of substitution and amylose/amylopectin ratio. The starch ethers having longer side chains failed to exhibit phase separation due to insufficient degrees of substitution. They generally possessed enhanced hydrophobicity relative to starch yet still had controllable numbers of free hydroxyl groups. The liquid crystallinity thus produced makes them ideal candidates for a novel processing technique designed specifically for permanently orienting main-chain, lyotropic, liquid-crystalline polymers.