Controlled polymer monolayer synthesis by radical transfer to surface immobilized transfer agents

Radical chain transfer from solution-generated free radicals to thiol transfer agents bound to the surfaces of planar silicon and silica particles was investigated as a method to generate surface-bound polymer brushes. Both conventional radical and reversible addition-fragmentation chain transfer (RAFT) polymerizations created polymer films with molecular weights dependent on the details of the reaction. In the presence of high free radical concentrations or RAFT agent modifiers, the surface had minimal influence on the growth of grafted polymer chains following the initial radical transfer to the surface. Notably, excellent control of film thickness was achieved in the absence of surface-bound initiators or RAFT agents, thereby simplifying the synthesis of immobilized brush architectures. On the other hand, low concentrations of solution free radicals in conventional radical polymerization generated grafted polymers with lengths varying considerably from polymers in solution. Despite the simplicity and versatility of this technique for creating polymer-modified surfaces by surface initiated polymerization (SIP), it has been under-utilized; likely due to the absence of a framework for the rational design of the brush. The details of this investigation should allow surface modification by polymer films to become accessible to researchers without the need to create complex precursor surface chemistries. © 2013 The Royal Society of Chemistry.