Synthesis and Properties of Crosslinked Polycarbosilanes by Hydrosilylation Polymerization

Abstract

The aim of this investigation is the development of crosslinked polycarbosilanes (PCSs) with excellence on mechanical properties. Crosslinked polycarbosilanes were obtained by using a hydrosilylation curing reaction between multi-functional vinylsilanes and hydrosilanes. The PCSs were prepared with a casting method from the monomer solution. The mechanical properties and the glass transition temperatures (Tgs) of the PCSs were measured by a flexural test and Differential Scanning Calorimetry (DSC). 29Si solid-state NMR spectroscopy was employed for estimating the conversion of the vinylsilanes. The effects of the following three points on the mechanical properties of the crosslinked PCSs were evaluated: (1) the molecular weight between the crosslinking points, (2) the introduction of flexural units, and (3) the network chain density. The mechanical properties and Tgs of the PCSs were found to be dependent on the structures of the monomer used. It was clear that both the high network chain density and the rigid-rod unit, [–Me2Si–p–C6H4–Me2Si–CH2CH2–], are favorable to high mechanical properties. The improvement in strength can be related to the structures of vinylsilanes and hydrosilanes used.