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Chain Transfer to Polymer and Branching in Controlled Radical Polymerizations of n ‐Butyl Acrylate
Author(s) -
Ahmad Nasir M.,
Charleux Bernadette,
Farcet Céline,
Ferguson Christopher J.,
Gaynor Scott G.,
Hawkett Brian S.,
Heatley Frank,
Klumperman Bert,
Konkolewicz Dominik,
Lovell Peter A.,
Matyjaszewski Krzysztof,
Venkatesh Rajan
Publication year - 2009
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200900450
Subject(s) - radical , branching (polymer chemistry) , chain transfer , radical polymerization , polymer chemistry , monomer , acrylate , polymer , chemistry , polymerization , chain termination , backbone chain , reversible addition−fragmentation chain transfer polymerization , photochemistry , organic chemistry
Chain transfer to polymer (CTP) in conventional free‐radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n ‐butyl acrylate (BA) has been investigated using 13 C NMR measurements of branching in the poly( n ‐butyl acrylate) produced. The mol‐% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short‐chain radicals which can be expected to undergo both intra‐ and inter‐molecular CTP at much higher rates than long‐chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short‐chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short‐chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization.