Initialization behavior at various target molecular weight RAFT‐mediated methyl acrylate polymerizations

Abstract

In the reversible addition‐fragmentation chain transfer (RAFT) mediated polymerization of methyl acrylate, a selective reaction is observed in the early stages of the polymerization. This initialization process was earlier observed in in situ 1H NMR spectroscopy experiments where extremely low target molar masses were chosen (around DP = 5). Here, for the first time, the presence of the initialization process is identified as the cause of an induction period under typical conditions of a RAFT‐mediated polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2500–2509, 2008

Living Radical Polymerization by the RAFT Process - A Second Update

“…AA [251] BA [251,252] BA [253] MA [54,252] St [254,255] HPA [251] St [256] SMe [251] BP/NPMI [257] S S 93 [216] BA [216] (BA) [216] S S 94* [255] AEP [87] BA [62,216] (BA) [216] TFPA [93] MMBL [258] AcS [259] St [260] St [261] PFS [93] NIPAM [262,263] St/MMBL [258] MMA/BA [62] BP/NPMI [257] BP/NMMI [257] BP/NEMI [257] TFPA-b-tBA [93] PFS-b-tBA [93] …”

“…The initialization process (consumption of the initial RAFT agent) in RAFT (co)polymerization has been studied by 1 H NMR spectroscopy for St/maleic anhydride (St/MAH) with RAFT agents 22 and 24, [53] methyl acrylate (MA) with RAFT agents 22, 24, and 92, [54] and of vinyl acetate (VAc) and Nvinylpyrrolidone (NVP) with xanthates 207, 209, and 211. [55] For many of these systems so-called selective initialization was observed in which there is substantial conversion of the initial RAFT agent into a single unit species before conversion into higher molecular weight chains.The effect is attributed to the rate constant of addition of the 'R' radical to MA being substantially slower than that for propagation.…”

“…For an efficient RAFT polymerization (Scheme 1, Fig. 3 22* [86] S S MA [54] AAEMA [87] MAEP [87] MMA [88,89] AEMA [90] DMAEMA [91] (TPMMA) [92] TFPMA [93] St [48,94,95] 277 [96] 278 [96] 392 [97,98] 345 [99] 348 [100] 347 [101] St [51] 364 [102] 365 [102] NVP [103] 385 [104] 386 [98] 387 [104] 388 [104] 389 [104] 390 [104] BA/ 407 [105] St/MAH [53] AAEMA-b-AEP [87] AAEMA-b-MAEP [87] MAEP-b-AAEMA [87] BMA/TMSEMA [106] TFPMA-b-tBA [93] St-b-NIPAM [95] St-b-HEMA/DMAEMA [86] 364-b-384 [102] 365-b-384 [102] 386-b-392 [97] 23* [107] S CN S DEGMA [108] EGMA [108] MAA [108] MMA [109] PEGMA …”

RAFT Polymerization – Then and Now

“…Selective initialization, the complete conversion of an initial low molecular weight RAFT agent to a species incorporating a single monomer unit is common to many well-behaved RAFT polymerizations (143)(144)(145)(146)(147)(148)(149) including those of styrene (143,146), methyl acrylate (145,148), N-vinylpyrrolidone (147) and vinyl acetate (147).…”

Molecular Weight and Tacticity of Oligoacrylates by Capillary Electrophoresis - Mass Spectrometry

“…[52,53] This controlled radical polymerization technique is based on a twostep addition-fragmentation mechanism using thiocarbonylthio compounds as transfer agents, although the precise mechanism is still under debate. [54,55] For instance, Klumperman et al [56][57][58][59] have investigated the early polymerization behaviour of several RAFT-mediated polymerizations. The period during which the initial RAFT agent was consumed was termed initialization, with different reaction behaviour observed before and after this period.…”