The effect of solvents on the structure and preperties of cast films of poly(r-benzyl glutamate) (PBLG) were studied. From X-ray diffraction measurements, it was found that films cast from dichloroethane, chloroform, and dichloromethane (called film A) had a well-ordered structure consisting of helices packed on a regular hexagonal lattice, while films cast from benzene and tetrahydrofuran (called film B) showed less crystallinity than film A. As for viscoelastic properties, film A showed peaks of tan iJ at 38 and 105°C (110 Hz). In the case of film B, the lower-temperature peak was shifted to a higher temperature and the peak was broadened. Film B further exhibited a remarkable decrease of modulus at about 135°C, which was accompanied with a small peak of tan iJ at this temperature. After being annealed at 140°C, film B showed a remarkable increase in its tan iJ peak at 105°C and simultaneously the lowertemperature peak shifted to 40°C and the peak at 135°C vanished. To elucidate these changes, differential thermal analysis (DT A) was performed. The DT A thermogram on film B showed an endothermic peak at 135°C, which was not observed after the film was annealed at 140°C. From the fact that the aggregates of superhelices of PBLG, which were precipitated from dimethylformamide solution by adding propionic acid, also showed an endothermic peak at 135°C, it is argued that the superhelical structure exists in the solid state of film B and stacks of benzene ring in the side chain are responsible for the characteristic behaviors of film B.

It has been reported that there is a special side chain-side chain interaction between the right-handed and left-handed a-helices in the racemic mixture of poly-(r-benzyl glutamate). In this paper physical properties of mixtures of poly(r-benzyl-Lglutamate) and poly(r-benzyl-n-glutamate) are studied. From X-ray diffraction measurements, the reflection characteristic of the regular arrangement of the benzyl group at the end of the side chain was shown to disappear on heating at 97°C and to appear on cooling at 73°C. This reversible change was also observed in viscoelastic, thermal and dilatometric measurements and was ascribed to the breakdown and formation of stacks of benzene rings. In the case of samples cast from benzene solution, it was found that the formation of stacks is hampered by the preferable superhelix formation. KEY WORDS Racemic Mixture I Poly(r-benzyl glutamate) I Stack I First-Order Transition I Physical Properties I

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