HIGHLY MOBILE CHARGE-CARRIERS IN POLY(DI-N-ALKYL)SILANES IN THE SOLIDAND IN THE MESOPHASE

Using the pulse-radiolysis TRMC technique the mobility and lifetime of radiation-induced charge carriers is studied in poly(di-n-alkyl)silan es with pentyl, hexyl and octyl sidechains in the solid and in the mes ophase. A lower limit for the sum of the mobilities of the positive an d negative charge carriers in the solid phase is estimated to be of th e order of 10(-5) m2V-1s-1. The mobility is found to be dependent on t he silicon backbone conformation. For the all-trans conformation the m obility is a factor of two larger than for the 7/3 helix conformation. At the I-->II transition to the conformationally disordered mesophase the mobility drops an order of magnitude or more. The lifetime of the mobile charge carriers is found to increase with increasing sidechain length.