EFFECTS OF TEMPERATURE AND CONCENTRATION ON THE STRUCTURES OF CHOLESTERIC LIQUID-CRYSTALS OF POLY(GAMMA-ALKYL L-GLUTAMATE)S

The cholesteric twist angle θ between two adjacent molecules was obtained as a function of temperature, concentration and side-chain length of poly (γ-alkyI L-glutamate)s (PALG). The samples used in this study were poly[γ-(ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and nonyl) L-glutamate]s abbreviated as PEtLG, PPrLG, PBuLG, PPeLG, PHxLG, PHpLG, POcLG and PNoLG, respectively, and their characterizations are shown in Table 1. The results were summarized as follows. (1) All concentrated solutions of PALG's in chloroform formed cholesteric liquid crystals. (2) With increasing the concentration, the 6 increased initially and then decreased after passing through the maximum value. The inter-molecular distanc corresponding to this maximum value was found to be extremely close to the distance which the side chains came into contact with each other. (3) As temperature increased, the θ value decreased in the solutions of PEtLG, PPrLG and PBuLG, on the other hand, it increased in the solutions of the other PALG's. It was found that the cholesteric helical sense was right-handed in the former and left-handed in the latter by measuring the sign of induced circular dichroism of Acridine Orange, an achiral dye dissolved in the cholesteric mesophase. (4) When the plus sign was given to right-handed cholesteric twist angle θ, the sign of δθ/δT was negative in all PALG's investigated. The above experimental results were compared with the current molecular theories based on the method of the electric multipole expansion. © 1979, The Chemical Society of Japan. All rights reserved.