Synthesis of NMP/RAFT inifers and preparation of block copolymers

Abstract

Two different initiator/transfer agents (inifers) containing an alkoxyamine and a dithiobenzoate were synthetized and used to trigger out either reversible addition‐fragmentation chain transfer (RAFT) polymerization or nitroxide‐mediated polymerization (NMP). α‐Dithiobenzoate‐ω‐alkoxyamine‐difunctional polymers were produced in both cases which were subsequently used as precursors in the formation of block copolymers. This synthetic approach was applied to N‐isopropylacrylamide (NIPAM) or polyethylene oxide methacrylate (EOMA) to form α,ω‐heterodifunctional homopolymers via RAFT at 60°C which were chain extended with styrene by activating the alkoxyamine moiety at 120°C. Under such temperature conditions, it is proposed that a tandem NMP/RAFT polymerization is initiated producing a simultaneous growth of polystyrene blocks at both chain‐ends. Self‐assembled nanostructures of these amphiphilic block copolymers were evidenced by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Living Radical Polymerization by the RAFT Process – A Third Update

“…A [280] St [280] PEGMA [280] (tBA) [280] 47 S S A* [281] St [171] (St-b-DMAEMA) [171] PEGA [281] (Continued ) C [282] MMA [282] …”

“…[616] The process requires RAFT agents or macro-RAFT agents with an electron withdrawing 'Z' group. Suitable 'Z' groups include 2-pyridyl (57, 70), phosphonate (282-284), or phenylsulfonyl (280). To achieve acceptable rates for reactions in organic solution, the reaction may be catalyzed by a Bronsted or Lewis acid, for example, trifluoroacetic acid or zinc chloride.…”

“…[280] These agents provided reasonable control over polymerization of St under RAFT conditions (608C, AIBN initiator) for low monomer conversions although dispersities broadened for higher monomer conversions. Poor control was observed in St polymerization under 'NMP conditions' (1208C).…”

Polymer Synthesis with More Than One Form of Living Polymerization Method

“…Guerrero‐Santos et al . prepared bis‐initiators containing an alkoxyamine and a dithiobenzoate to combine NMP and RAFT polymerization ( Table 7 ).…”

“…Guerrero-Santos et al [186][187][188][189] prepared bis-initiators containing an alkoxyamine and a dithiobenzoate to combine NMP and RAFT polymerization ( Table 7). The NMP/RAFT bis-initiators led to the synthesis of a series of block copolymers including…”