Interfacial tension between coexisting isotropic and nematic phases for a lyotropic polymer liquid crystal: Poly(n-hexyl isocyanate) solutions

The interfacial tension gamma between the coexisting isotropic and nematic phases of toluene solutions of poly(n-hexyl isocyanate) (PHIC) was determined as a function of the molecular weight of PHIC by the pendant drop method. The value of gamma was almost independent of the molecular weight, in contrast to the theoretical prediction for rodlike polymer solutions that gamma should be inversely proportional to the polymer molecular weight. This is consistent with the disagreement between rod theories and experiment with respect to the isotropic-nematic binodal concentrations of PHIC solutions and implies the importance of the chain-flexibility effect on gamma in the solutions.