Wk. Busfield et al., END-FUNCTIONALIZED COPOLYMERS PREPARED BY THE ADDITION-FRAGMENTATION CHAIN TRANSFER METHOD - STYRENE-METHYL METHACRYLATE SYSTEM, Polymer, 40(2), 1999, pp. 389-396
Co-oligomers and copolymers of styrene and methyl methacrylate have be
en prepared by free radical polymerisation in the presence of the chai
n transfer agent ethyl-alpha-(t-butanethiomethyl) acrylate. Chain tran
sfer constants are not significantly influenced by the co-monomer comp
osition and lie in the range 0.47-0.90. Bulk copolymer composition is
independent of the amount of chain transfer agent in the higher MW ran
ge (> 20 000). In contrast, the styrene content of lower MW oligomers
extracted by fractional precipitation decreases with decreasing MW bel
ow about 1000. The efficiency of the addition-fragmentation mechanism
in producing specifically end-functionalised co-oligomers (MW < 5000)
was investigated by H-1 n.m.r. spectroscopy. Spectral peaks are mostly
consistent with the expected end groups for all co-monomer feed syste
ms. Quantitative consistency of end group concentrations is also good
for co-oligomers with MW > 1500. At lower MWs, there is an increasing
deficiency in olefinic end groups and a high ester group concentration
relative to that expected from the MW. (C) 1998 Elsevier Science Ltd.
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