A gamma -benzyl glutamate- gamma -alkyl glutamate copolymer having the general formula (I) <IMAGE> (I) wherein; R is C10-30 alkyl group, m and n are 50</=m+n</=2,000 and m/n=80-10/20-90, and benzyl ester unit and alkyl ester unit are either both L-forms or both D-forms.
Thermotropic cholesteric liquid crystalline polypeptide comprising alpha-benzyl glutamate-alpha-alkyl glutamate copolymer