Monolayers of copoly(gamma-methyl L-glutamate-co-gamma-hexyl L-glutamate)s (copoly(MLG-HLG)s) at the air-water interface were examined by the surface pressure measurements and FTIR spectroscopy to understand the liquid crystal behavior of synthetic polypeptides with flexible side chains. Surface pressure-area isotherms showed the formation of a liquid-expanded state in the region of intermediate hexyl content. Surface compressional moduli showed higher fluidity of the copolymers. The copoly(MLG-HLG)s with hexyl contents around 30-80 mol % indicated a two-dimensional packing and orientation different from that of the constituent homopolymer. Polarized IR spectra of LB films of these polypeptides indicated that the poly(glutamate) molecules in alpha-helix were deposited with a mean orientation parallel to the barrier used to compress the monolayer and that the alkyl side chains were randomly oriented around the alpha-helical rod. The present data suggest that the radial distribution of the hexyl side chains in the alpha-helical molecules plays the role of a solvent in the formation of liquid crystals in the copolypeptides.