CRYSTAL STRUCTURE OF POLY-(SODIUM-L-GLUTAMATE) (PSLG) IN OPTICALLY ANISOTROPIC STATE

Abstract

The changes of crystal form and lattice spacings observed for the concentrated aqueous solution of PSLG were studied.At the PSLG concentration lower than 60% the crystal form determined from the X-ray diffraction patterns in anisotropic state was pseudo hexagonal. The lattice spacings became shorter with increasing concentration in the range from 48% to 60% and did not change in the PSLG concentration lower than 48%. The relationship between the concentration of PSLG, C in volume fraction and the length of a-axis of hexagonal unit cell, a in Å, was represented by the following formula with a constant KC=K/a2The structure of anisotropic PSLG solution below 60% concentration may be regarded as a nematic liquid crystal.At the PSLG concentration higher than 70%, the crystal form was assigned to the orthorhombic unit cell. The dimensions for 80% PSLG were determined for the rolled film as a=9.26 Å (direction of hydrogen bond) b=13.13 Å (direction of side chain) c=6.7 Å (fiber period).As the diffraction spot corresponding to the fiber period was not observed, c value was assumed as above.b value, the distance between (0k0) planes, became shorter with increasing concentration of PSLG, and a value, the distance between (h00) planes, did not change with the concentration. These results were explained by the reduction of lattice spacings due to the decrease in water content between the β-sheets.