AbstractMacromolecular aggregation during thermoreversible gelation in solutions of the helical polypeptide poly(γ‐benzyl‐L‐glutamate) PBLG in benzyl alcohol BAwere studied by small angle neutron and small angle X‐ray scattering. Gelation is apparent as a large increase in the intensity scattered at low angles, signifying formation of a microfibrillar PBLG network. The aggregated phase in isotropic gels from semidilute solutions contains about 28 solvent. A periodic structure is observed when gelation is induced by rapid cooling to a low temperature, but not by slow cooling or gelation at a higher temperature. In gels from concentrated liquid crystal solutions, two crystalline structures are observed, depending on whether the solution is rapidly quenched and then annealed or slowly gelled at an elevated temperature. A phase diagram for the PBLG/BA system is presented and the observed microstructural transitions are rationalized in terms of a gelation mechanism involving a combination of liquid‐liquid phase separation and crystallization in the form of polymer‐solvent
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