Synthesis and Spinnability of the High Softening-point Polycarbosilane†

Abstract

Polycarbosilane(PCS) was synthesized by polydimethylsilane as starting material via high-temperature-normal-pressure method. The characteristics of polycondensation reaction and the increase mode of molecular weight were investigated by changing the reaction conditions. Moreover,the relationship between structure and spinnability of PCS was discussed. The results show that the condensation reaction of PCS at high temperature can occur in two different ways,the steady growth of molecular weight and the accelerated growth of molecular weight,corresponding to the polycondensation reaction between molecule of PCS with different molecular weights. The PCS obtained by steady growth pattern had a bimodal molecular weight distribution which possessed good spinnability. However,PCS formed by the accelerated growth model contained too much branching structures,which exhibited multi peak molecular weight distribution and poor spinnability. High softeningpoint PCS(256—287 ℃) with a number average molecular weight of 2. 3 × 103 and good spinnability was successful synthesized by polycontrolling the polycondensation reaction condition to make it progress in the steady growth model.