Homogeneous free-radical polymerization of styrene in supercritical CO2

✍ Scribed by Sabine Beuermann; Michael Buback; Christoph Isemer; Almut Wahl

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 86 KB
• Volume: 20
• Category: Article
• ISSN: 1022-1336
• DOI: 10.1002/(sici)1521-3927(19990101)20:1<26::aid-marc26>3.0.co;2-2

✦ Synopsis

The free-radical polymerization of styrene has been studied in the homogeneous phase of supercritical (sc) CO 2 at 80 8C and pressures between 200 and 1 500 bar. 2,29-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.