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Controlled free radical photopolymerization of styrene initiated by trithiocarbonate
Author(s) -
Ran Rong,
Wan Tao,
Gao Tao,
Gao Jian,
Chen Zhi
Publication year - 2008
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2307
Subject(s) - photopolymer , chain transfer , polymerization , copolymer , radical polymerization , polymer chemistry , dispersity , reversible addition−fragmentation chain transfer polymerization , materials science , photochemistry , chemistry , polymer , organic chemistry
Density functional theory calculations are reported for prediction of the trends in CS bond dissociation energies and atomic spin densities for radicals using S , S ′‐bis(α,α′‐dimethyl‐α‐acetic acid) trithiocarbonate (TTCA) and bis(2‐oxo‐2‐phenylethyl) trithiocarbonate (TTCB) as reversible addition fragmentation chain transfer (RAFT) reagents. The calculations predict that the value of the CS bond length (1.865 Å) of TTCA is longer than that (1.826 Å) of TTCB, and TTCA is more effective for the polymerization of styrene (St) compared to TTCB as predicted by density functional theory. In photopolymerizations, pseudo‐first‐order kinetics were confirmed for TTCB‐mediated photopolymerization of St due to the linear increase of ln([M] 0 /[M]) up to about 28% conversion, suggesting the living characteristics behavior of the photopolymerization of St in the presence of TTCB. For both TTCA and TTCB the polydispersities change with increasing conversion in the range 1.10–1.45, typical for RAFT‐prepared (co)polymers and well below the theoretical lower limit of 1.50 for a normal free radical polymerization. In addition, the triblock copolymer polystyrene‐ block ‐poly(butyl acrylate)‐ block ‐polystyrene (PSPBAPS) was successfully prepared, with very good control over molecular weight and narrow polydispersity ( M w / M n = 1.45), using PSSC(S)SPS as macro‐photoinitiator under UV irradiation at room temperature. This indicated that this reversible and valid strategy led to a better controlled block copolymer with defined structures. Copyright © 2007 Society of Chemical Industry