Growing crosslinker: Gel synthesis using novel divinyl crosslinker with expanding chain-length between vinyl groups by RAFT polymerization

Abstract

In order to manage the network structure of vinylic polymer gels, a novel afunctional divinyl-crosslinker (dv-CTA) was designed by introducing a trithiocarbonate (TTC) group. This functionalized crosslinker could grow to extend the chain-length between two vinyl groups throughout the gelation reaction, since the TTC group functions as a chain transfer agent for reversible addition-fragmentation chain transfer (RAFT) polymerization. This growing crosslinker was found to lead to the improvement of crosslinking efficiency in poly(N-isopropylacrylamide) (PNIPAAm) gel synthesis by RAFT polymerization in combination with a conventional crosslinker, N,N′-methylenebisacrylamide (BIS). This result can be explained by reduced steric hindrance between the network chain and the vinyl group, originating from the crosslinker, when the crosslinker grows. Therefore the growing chain allows enhanced crosslinking.