A. Ciferri

Mesophase formation by semirigid polymers: (poly(n-hexyl isocyanate) in 1-chloronaphthalene

A study of the persistence length q and of the critical polymer volume fraction v′2 at which the mesophase appears for poly(n-hexyl isocyanate) (PHIC) in 1-chloronaphthalene is presented. The phase diagram was determined over the temperature range 80 to 188°C, corresponding to v′2 from 0.2 to 1.0. The thermal expansion of the system is accounted for in evaluating v′2 and the axial ratio of the Kuhn segment, 2qd. As reported for PHIC in toluene, and for several cellulose derivatives, the limiting value of v′2 at large molecular weight can be represented rather well by the Kuhn chain model with a temperature-dependent Kuhn segment length. However, while the thermotropic effect is adequately described by the temperature coefficient of q, the experimental v′2 is somewhat smaller than predicted.