ABSTRACT:A series of poly(r-methyl o-glutamate) (PMDG) films with the different structures were systematically prepared from dichloromethane (DCM)-N, N-dimethylformamide (DMF) solutions. The structures of these films were classified into three types, vix., phase I, phase M, and phase C as obtained in a previous work from DMF, 1, 2-dichloroethane and DCM, respectively. Observation of the PMDG films cast from ch!oroform-DMF solutions, showed that phase C arises from the phase which consists of the cholesteric liquid crystal structure, and it was assumed that the crystallites in phase C should be divided into mosaic blocks. Three mechanical dispersions were observed at 160, 190°C, and above 200°C. The a1 dispersion (at 160°C) was associated with the molecular relaxation in phase I, and further, the a 3 dispersion (above 200°C) was related to the molecular motion of a-helices in phase M with the cholesteric twisted structure. For the a2 dispersion (at 190°C) commonly observed for phase C, two relaxation mechanisms are discussed: the molecular motion of ahelices in phase C and the mutual displacement of the neighboring crystallites. The PMDG films cast from m-cresol at various temperatures and the PMDG-poly(r-methyl L-glutamate) (PMLG) blend films cast from chloroform solutions, showed a remarkable shift of a 2 loss peak temperature. To explain this shift in peak temperature, the latter mechanism seems reasonable for the a 2 dispersion.KEY WORDS Poly(r-methyl glutamate)/ Casting History/ Cast Film/ Mechanical Dispersion / X-Ray Diffraction / Depending on the solvent and polypeptide concentration, a polypeptide molecule may exist in a number of conformations in solution. 1 Solvents are categorized into random coil and helical types. The random coil solvents are generally very polar and form strong hydrogen bonds with the polypeptide molecules. Dichloroacetic acid (DCA) and trifluoroacetic acid (TFA) are random coil solvents for many polypeptides in dilute solution. Most chlorinated hydrocarbons such as chloroform and DCM, with DMF and m-cresol, favor formation of the helical form of the polypeptide. chain structure has been observed in the films swollen in formic acid and in crystals precipitated from dilute solution containing formic acid. 2 This structure is also obtained from TFA or DCA solution, depending on the casting velocity. 3 Thus, when the films are cast from random coil solvents, the chain conformation in the films is not only in the helical form, but also partially in the /3-chain form.Poly(r-methyl glutamate) is known to be soluble also in the coil form in such solvents as DCA and TF A, and in the helical form in helicogenic solvents such as m-cresol and chloroform. However, when films are prepared from random coil solvents, the chain conformation in the films is mainly in the helical form. On the other hand, the /3-No conformational change is observed when the films are cast from the helicogenic solvents. Thus, in this solvent system, the association or aggregation of a-helices 4 -6 is of interest. In a...

Elastic moduli of crystal lattices ofpoly(y-benzyl glutamate) films with uniplanar orientation were measured by the X-ray diffraction method in a direction perpendicular to the film surface, i.e., to the a-helical axis. Three types of specimens were prepared by casting dichloroethane solution of the polymer: forms Band C of the L-polymer, and the racemic mixture. Forms Band C showed irreversible lattice deformations around room temperature after the removal of the loads, but the racemic form did not. The lattice moduli due to reversible strain were measured at 0-60°C in the range of 1.5-0.5 GPa. The values were comparable to the macroscopic specimen moduli measured by dynamic mechanical measurement. The decrease in lattice moduli around room was attributed to the side-chain dispersion.