Phosphorus-Containing Gradient (Block) Copolymers via RAFT Polymerization and Postpolymerization Modification.

Reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene (St) and 4-(diphenylphosphino)styrene (DPPS) is explored to establish the statistical distribution of the phosphine-functional monomer within the copolymer. RAFT copolymerization of St and DPPS at a variety of feed ratios provides phosphine-functional copolymers of low dispersity at moderate monomer conversion ( Ð < 1.2 at conv. >60%). In all cases, the fraction of DPPS in the resulting polymers is greater than that in the monomer feed. Estimation of copolymerization reactivity ratios indicates DPPS has a strong tendency to homopolymerize while St preferentially copolymerizes with DPPS ( rDPPS = 4.4; rSt = 0.31). The utility of the copolymers as macro-RAFT agents in block copolymer synthesis is demonstrated via chain extension with hydrophilic acrylamide ( N, N-dimethylacrylamide (DMAm)) and acrylate (poly(ethylene glycol) methyl ether acrylate (mPEGA), and di(ethylene glycol) ethyl ether acrylate (EDEGA)) monomers. Finally, access to polymers containing phosphine oxide and phosphonium salt functionalities is shown through postpolymerization modification of the phosphine-containing copolymers. [ABSTRACT FROM AUTHOR]