Grafting on polysilanes using transfer radical polymerisation

Atom transfer radical polymerisation (ATRP) was used in an attempt to prepare a graft polymer based on poly(methylphenylsilane) (PMPS). A partially bromomethylated PMPS was subjected to ATRP conditions in order to grow poly(methyl methacrylate) (PMMA) grafts onto that backbone. Following the grafting reaction, a substantial increase in molecular weight was observed by size exclusion chromatography, analysis using refractive index detection. However, a bimodal product molecular weight distribution was observed using a UV detector set at wavelengths at which only the PMPS backbone can be detected. The lower molecular weight fraction was identified as homopolymeric PMPS although it appears to include some material with short grafts, while the higher molecular weight fraction corresponds to PMPS with long grafts. These observations are interpreted as the formation of a substantial amount of PMMA that is not grafted onto PMPS through a radical process initiated independently of the ATRP. However, since MMA is barely susceptible to thermal polymerisation, this is not easily rationalised. (C) 2002 Society of Chemical Industry.