Porous, functional, poly(styrene-co-divinylbenzene) monoliths by RAFT polymerization

Herein we provide the first report of a new method for the preparation of porous functional poly(styrene-co-divinylbenzene) monoliths by use of reversible addition-fragmentation chain transfer (RAFT) polymerization. The method, exemplified by styrene-divinylbenzene copolymerization in the presence of 2-cyano-2-propyl dodecyl trithiocarbonate, provides control over polymerization kinetics, monolith morphology and surface functionality. Kinetic studies of monolith formation show a period of slow copolymerization, with a rate similar to RAFT homopolymerization of styrene, followed by rapid copolymerization, with a rate similar to that observed in conventional styrene-divinylbenzene copolymerization. The time to onset of rapid polymerization (gelation) and the monolith morphology depend strongly on the RAFT agent concentration. The RAFT-synthesized monoliths show a modified morphology with smaller pores and polymer globules when compared to non-RAFT monoliths, but importantly retain good flow properties. Retention of the thiocarbonylthio group within the monolith structure in an active form for surface-functionalization of the polymeric monoliths is demonstrated by the successful RAFT "grafting from" polymerization of (4-vinylphenyl)boronic acid. These functional monoliths have potential applications in chromatography and flow chemistry.