A Bipedal Silica-Immobilized Azo-Initiator for Surface-Confined Radical Polymerizations

The present study introduces the silica-anchored azo-initiator 4,4'-azobis(4-cyano-N-(3 '-triethoxysilylpropyl)-valeric amide) (ACTA) for the surface-initiated polymerization of methyl acrylate (MA) with and without additional grafted reversible addition-fragmentation chain transfer (RAFT) agents 1,4-bis(3'-trimethoxysilylpropyltrithiocarbonylmethyl)benzene and 1,6-bis(o,p-2'-trimethoxysilylethylbenzyltrithiocarbonyl)hexane. While the sole use of silica-linked ACTA produced grafted poly(methyl acrylate) (pMA) of high molecular weight, due to a 2D Trommsdorff effect, the polymerization in combination with the fixed RAFT agents exhibited living behaviour with increasing molecular weights during polymerization. Silica-pMA hybrids were further analyzed via thermogravimetric analysis and scanning electron microscopy, which revealed significant differences between the three approaches.