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Homogeneous free‐radical polymerization of styrene in supercritical CO 2
Author(s) -
Beuermann Sabine,
Buback Michael,
Isemer Christoph,
Wahl Almut
Publication year - 1999
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/(sici)1521-3927(19990101)20:1<26::aid-marc26>3.0.co;2-2
Subject(s) - styrene , supercritical fluid , azobisisobutyronitrile , polymerization , polystyrene , radical polymerization , chain transfer , polymer chemistry , bulk polymerization , supercritical carbon dioxide , monomer , chemistry , dispersion polymerization , materials science , solution polymerization , copolymer , polymer , organic chemistry
The free‐radical polymerization of styrene has been studied in the homogeneous phase of supercritical (sc) CO 2 at 80°C and pressures between 200 and 1 500 bar. 2,2'‐Azobisisobutyronitrile is used as initiator and CBr 4 as chain‐transfer agent. The polymerization is monitored by means of online FT‐IR/NIR spectroscopy. In the presence of CO 2 a solution polymerization may be carried out up to a considerable degree of monomer conversion. At 500 bar, for example, maximum styrene conversions of 34.4 and 11.9% may be reached in homogeneous phase at CO 2 contents of 16.8 and 44.5 wt.‐%, respectively. Analysis of the measured conversion‐time profiles yields termination rate coefficients, k t , which are by one order of magnitude larger than k t for styrene bulk polymerizations at identical temperature and pressure. The enhanced termination rate in fluid CO 2 is assigned to the poor solvent quality of scCO 2 for polystyrene.