Heterogeneous network polymers. VI. Effects of rate of solvent evaporation on residual PGA liquid crystal structure and its dynamic mechanical properties

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Abstract
Domains of cholesteric liquid crystal structures exist in films of heterogeneous network polymers from poly(L‐glutamic acid) (PGA) and poly(oxyethylene glycol) (PEG M̄n = 302, 1003). The sizes and the amounts of the domains are dependent on the PGA content, the evaporation rate of the solvent, and the molecular weight of PEG. At the PGA content of 40% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities increase with increase in the rate of solvent evaporation. These observations suggest that the phase separation of PEG takes place at a PGA content of 40% when the evaporation rate is small. On the other hand, at a PGA content of 70% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities vary little with decrease in the rate of solvent evaporation. These observations suggest that PEG molecules are accommodated among α‐helices of PGA and that the cholesteric liquid crystal phase grows at a PGA content of 70% when the evaporation rate is small.