Using linear and branched polysilanes for the photoinitiated polymerization of a commercial silicone-acrylate resin.: A real time FTIR study

The photo-crosslinking of a silicone-based oligomer, bearing pendant acrylate groups, has been carried out using linear polysilanes (poly(methyl phenyl silane), poly(methyl- n-propyl silane), poly(di- n-hexyl silane)) and a branched one, poly( p-butylphenyl phenyl silane-co-phenyl silyne), as initiators. The curing rate was measured with the aid of the real time Fourier transformed infrared spectroscopy. Apart from the neat oligomer also formulations containing reactive diluents, i.e. acrylic and vinyl ether monomers were photo-cured. An excellent curing performance (final conversion of about 95%) was achieved with a 1:1 (w:w) blend of the oligomer with 2-ethyl hexyl methacrylate (EHMA). n-Butyl vinyl ether (BVE) was found to copolymerize with the pendant acrylate groups. Moreover, in the presence of diphenyl iodonium chloride it homopolymerized simultaneously by a cationic mechanism. In this way interpenetrating structures were formed. The iodonium ions oxidize some of the photo-generated silyl radicals thus producing initiating cations.