Coexistence of two liquid crystalline phases in poly(γ-benzyl-α, L-glutamate) solutions

Abstract

IN 1956, Flory¹ proposed a phase diagram for rod-like molecules of the form shown in Fig. 1. Since then, most of the major features of this diagram have been verified experimentally². In particular, the two-phase 'chimney' is now well established. One feature that has not previously been established, however, is the slight maximum (the 'cap') in the phase boundary on the high-concentration side of the chimney. Flory¹ pointed out that this cap should manifest itself as two coexisting liquid-crystalline (anisotropic) phases. Here we provide evidence for bulk phase separation into two such phases in a macroscopic (∼0.5 g) liquid-crystal sample held in a constant-temperature bath. A distinct boundary can be seen between the two phases, and they are distinguished further under an optical polarizing microscope.