Effect of the nature of the substituents on the temperature region of existence of the mesomorphic state in transtactic cyclo-linear polymethyl(phenyl)siloxanes

Transtactic cyclo-linear methyl(phenyl) siloxane polymers and copolymers forming a mesomorphic phase over a wide temperature range have been synthesized. On the basis of data from differential scanning calorimetry and X-ray diffraction analysis, the phase diagrams for different numbers of phenylgroups in the repeating unit are derived and the values of T g and T m are compared with the corresponding values for linear polydimethyl- and polydiphenyl-siloxanes An increase in the number of phenylgroups in the repeating unit is accompanied by an increase in the heat of melting and a decrease of the heat of isotropization.