SAN-b-P4VP block copolymer synthesis by chain extension from RAFT-functional poly(4-vinylpyridine) in solution and in emulsion
Reversible addition fragmentation chain transfer (RAFT)-mediated polymerization was successfully applied for the synthesis of poly(4-vinylpyridine) (P4VP) polymers of predetermined molar mass and of low polydispersity index. These RAFT end-functionalized polymers were then used as macro-RAFT agents and further chain extended with an azeotropic mixture of styrene (STY) and acrylonitrile (AN) (63 mol% STY). Initially, these chain extension experiments were carried out in solution. In that case, the formation of the P4VP-b-SAN block copolymers clearly demonstrated the large fraction of chain end functionality in these RAFT-functional P4VP polymers. Proof of the formation of low molar mass P4VP-b-SAN block copolymer was obtained by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Gradient polymer elution chromatographic (GPEC) analysis confirmed successful formation of P4VP-b-SAN block copolymers. Block copolymer synthesis in emulsion was also investigated. The polymerization mediated by a RAFT-functional P4VP, macro-RAFT agent, was carried out as a semicontinuous process. The complete transformation of the P4VP starting block into P4VP-b-SAN block copolymer points to an efficient control of the polymerization in emulsion. This procedure leads to the formation of a colloidally stable latex. The results of GPEC analysis confirmed the successful block copolymer latex formation. © 2007 American Chemical Society.