Thermo-optical investigations of polysiloxane/liquid crystal mixtures

Thermo-optical properties of poly(dimethylsiloxane)/liquid crystal and poly (methylphenylsiloxane)/liquid crystal blends are investigated. Two low mole cular weight liquid crystals are considered: 4-cyano-4'-n-pentyl-biphenyl o r 5CB and the eutectic mixture of cyanoparaphenylene derivatives known as E 7. Equilibrium phase diagrams are established by polarized optical microsco py and analyzed within mean field theories of isotropic mixing and nematic order. Effects of the methyl-phenyl substitution, the nature of liquid crys tal and the polymer molecular weight on the phase diagram are discussed.