Permeability of benzene through polyfy-benzyl L-glutamate) (PBLG) film was found to be dependent on the solvent used for casting the membrane. Thin films of PBLG were cast from methylene chloride and benzene solutions. Permeability of benzene (liquid) through these membranes was measured at different concentrations of benzene, using heptane as diluent. Although the solubility coefficient of the film cast from benzene was only -~18% higher than that of the film cast from methylene chloride (densities being identical), the diffusion coefficient of benzene at infinite dilution, D0, of the former film exceeded that of the latter one by ~550%. These data indicate differences in the morphology of the membranes. The origin of these differences has been related to the different lyotropic solutions (cholesteric in the case of PBLG in methylene chloride and probably smectic in the other case) from which these films were cast.

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SynopsisThe effect of casting solvent on the material properties of poly(y-methyl-D-glutamate), PMDG, was investigated. The specific solvents used were chloroform, trifluoroacetic acid, dichloroacetic acid, methylene chloride, hexafluoroisopropanol, and tetrachloroethane. The different nature of these solvents controlled the degree of a, 8, or random coil contents of the final film. The effect of the morphology on material properties induced by the respective solvents was investigated by dynamic mechanical measurements of the dry films, stress strain behavior of both wet and dry films as well as by wide-angle x-ray diffraction, small-angle light scattering, and optical microscopy. Infrared spectroscopy was used to help determine a or 0 content. It was found that the casting solvent has considerable influence on material behavior and morphology. These differences are reflected in both the dynamical mechanical (small strain) and stressstrain (large strain) measurements as well as the x-ray scattering and optical microscopy. It was noted by light scattering that all films gave rise to anisotropic rod scattering with the exception of the 6 film cast from trifluoroacetic acid. This latter film appeared to be optically isotropic.