Summary
Poly(γ-benzyl l-glutamate) (PBLG) exists in the rodlike α-helical conformation and forms a thermoreversible gel in benzyl alcohol (BA). Phase diagram of the system PBLG/BA was investigated. The gel network comprises crystalline aggregates. There are two types of aggregated structures depending on the gelation temperatures; one (A) is the so-called complex phase (volume fraction of polymer is 0.76), and the other (B) is the crystal containing few solvent molecules. Melting temperatures of B type gels (in the range of 62–70°C) are slightly higher than those of A type gels. Above the gel-sol transition temperature, the solution forms a cholesteric liquid crystal, provided the polymer concentration exceeds about 15 vol%. Mechanism of the formation of A and B was discussed in the phase diagram.
The solution with concentration between 10 and 20 vol % (depending on molecular weight) contains the isotropic and anisotropic phases at equilibrium. The composition and fractionation effect within conjugate phases were investigated at 80 °C for solutions containing two PBLG samples differing in molecular weights. The biphasic region was widened by mixing the two PBLG samples, and the isotropic phase showed a tendency to exclude the high-molecular-weight fraction.
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Sasaki, S., Tokuma, K. & Uematsu, I. Phase behavior of poly(γ-benzyl L-glutamate) solutions in benzyl alcohol. Polymer Bulletin 10, 539–546 (1983). https://doi.org/10.1007/BF00285373
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DOI: https://doi.org/10.1007/BF00285373