BIAXIAL EFFECTS IN NEMATIC COMB-LIKE POLYMERS

Comb polymers consisting of semiflexible main chains and rodlike side chains form complex nematic phases, largely as the result of competition between polymer entropy and the nematic order of the component parts of the molecule. The competitive effects are modeled by choosing different molecular architectures and thus different strengths of molecular inteactions. The molecular interactions are chosen to have the simplest possible form and are modeled using a mean field theory. The five nematic phases found are called N(I), N(II), N(III), N(IB), and N(IIB). The N(I),N(II), and N(III) phases are uniaxial and have at least one component, main or side chain, ordered in a particular direction. The biaxial phases N(IB) and N(IIB) have each component ordered in directions perpendicular to each other. This has unusual consequences, resulting in the symmetry of the component order parameters being lower than that of the component interactions. Consequently the main-chain conformation becomes anisotropic in three directions. These biaxial phases represent intermediate states as architecture is varied between the uniaxial states N(I) and N(II).