THE EFFECT OF PHASE-TRANSFER CATALYSTS ON POLYSILANE FORMATION

Polysilanes are most often prepared by a Wurtz-type coupling of organodichlorosilanes with sodium metal in refluxing toluene. The addition of a catalytic amount of crown ether to the reaction mixture was found to increase the rate of disappearance of the monomer with increasing crown ether concentration, suggesting that anionic species are involved in the polymerization mechanism. Higher yields of polymer relative to cyclic material were obtained, and the polymer displays a monomodal distribution. Better reproducibility of the yields and molecular weight of the polymers can be achieved. The presence of cryptand was found to have similar effects although some degradation of the polymer upon continued refluxing of the reaction mixture was observed. Degradation experiments on poly(n-hexlymethylsilane) with sodium in refluxing toluene showed that the polymer degraded to cyclics in a few minutes with cryptand but not with crown ether.