Poly(silylenemethylenes) - A novel class of organosilicon polymers

The synthesis and investigation of the poly(silylenemethylene)s, linear polymers with a regular -RR'SiCH2- repeat unit, are reviewed, particularly from the standpoint of recent work carried out in the authors' own laboratory in the past few years. Improvement in the synthetic routes to the substituted disilacyclobutanes used as monomers in the ring-opening polymerization process employed for the synthesis of these polymers has enabled the preparation of a wide range of new polymers of this type. This range of polymers has been extended further by using reactive functionalities on Si in polymers containing Si-Cl, Si-OR and Si-H groups to append various side chains on to the polymer backbone. The parent polymer in this series, polysilaethylene, has been studied as an analog of polyethylane and as a precursor for silicon carbide, leading to information about the crystalline structure for the solid form of this polymer, as well as on the polymer-to-ceramic conversion process. The ethoxy-substituted polymer, [Si(OEt)(2)CH2](n), undergoes hydrolysis and condensation on treatment with water to produce a gel which has an inorganic (Si-O-Si)/organic (Si-CH2-Si) network structure. Upon pyrolysis to 1000 degrees celcius, this gel is converted into a silicon oxycarbide having a full distribution of SiC4-x O-x (x=0-4) microenvironments.