LIQUID CRYSTALLINITY IN PARASUBSTITUTED POLY GAMMA-BENZYL-L-GLUTAMATES

The liquid crystalline behavior of poly gamma-p-fluorobenzyl-L-glutamate, poly gamma-p-trifluoromethylbenzyl-L-glutamate, poly gamma-p-nitrobenzyl-L-glutamate, and poly gamma-benzyl-L-glutamate has been investigated. The first two polymers are new materials while the synthesis of the latter two has been reported in the literature. Only the liquid crystalline properties of poly gamma-benzyl-L-glutamate have been previously reported and this study was initiated in order to determine if electron withdrawing substituents in the para position would influence the liquid crystal behavior of these polymers. Poly gamma-benzyl-L-glutamate was used as the reference standard to which the other three were compared. Under the experimental conditions employed, the equispacings for poly gamma-benzyl-L-glutamate were 4-6 mum, poly gamma-p-fluorobenzyl-L-glutamate, 6-8 mum, poly gamma-p-trifluoromethylbenzyl-L-glutamate, 7-9 mum, and poly gamma-p-nitrobenzyl-L-glutamate, 11-15 mum. The equispacings for the para nitro polymer show the largest difference from the unsubstituted benzyl ester polymer, with approximately twice the value than that for poly gamma-benzyl-L-glutamate. The results of this study have shown that, in the poly glutamic acid benzyl ester system, the presence of a strong electron withdrawing group in the para position of the benzyl function does influence the liquid crystal properties of this polymer system.