Occurrence of β‐chain conformation in poly‐γ‐methyl glutamate membranes

Molecular chain conformations of poly‐γ‐methyl‐L‐glutamate, poly‐γ‐methyl‐D‐glutamate, and poly‐γ‐methyl‐D,L‐glutamate in membranes prepared by using mainly trifluoroacetic acid and formic acid as solvents were investigated by infrared, X‐ray diffraction, and optical rotatory dispersion measurements. It was pointed that these polymers exist in the α‐helix form in membranes cast from trifluoroacetic acid solutions, but in the β‐chain form in membrances swollen in formic acid. The β‐chain structure was also observed in crystals precipitated from dilute solutions including formic acid. The formation of the β‐chain structure was discussed.