CHARGE-CARRIER MOBILITIES IN LIQUID-CRYSTALLINE MESOMORPHIC POLY(DI-N-ALKYLSILYLENE)S - INFLUENCE OF BACKBONE CONFORMATION

The charge transport properties of a series of symmetrically substitut ed mesomorphic poly(di-n-alkylsilylene)s are studied using the pulse-r adiolysis time resolved microwave conductivity (PR-TRMC) technique. Th e observed conductivities for these polymers could be correlated with different backbone conformations present both in the crystalline solid phase and in the liquid crystalline mesophase. The transition from th e solid phase to the mesophase is accompanied by a disordering of the silicon backbone that results in a decrease of the conductivity of up to two orders of magnitude. The charge carrier mobilities found varied from 5x10(-5) m(2)/Vs for the all-trans conformation in the solid pha se to 6x10(-7) m(2)/Vs for the disordered backbone conformation in the mesophase. The anisotropic radiation-induced conductivity observed fo r aligned poly(di-n-hexylsilylene) samples demonstrate that charge car rier migration takes place preferentially in the direction of the poly mer backbone.