Polymerization of styrene in solution and supercritical CO2

ABSTRACT Supercritical (SCF) fluids are effective solvents due to their liquid-like densities and solvation power, and gas-like viscosities and diflusivities. Separation processes based on supercritical fluids are used widely aş alternative processes to conventional separation processes, since the solvation^ power of supercritical fluids vary with temperature and pressure. In supercritical separation processes, carbon dioxide jg the most preferred supercritical fluid, because it is nonflammable, nontoxic, readily available and Inexpensive, and has a low critical temperature and a rrioderate jcritieal pressure. Supercritical CÖ2 is also used ia polymerization to achieve product of good quality and to eliminate nontoxic solvents. In this study, polydHnethylsiloxane (PDMS) based macroazd initiator was synthesized using 4,4 -a2obis-4Tçyanopentaâoyl chloride (ACPC) and PD^dS. Using this initiator., jree radical polymerization of styreije in supercritical C02 was carried out at 300-400 bar, 60-70°C, 5- 15% initiator concentratibns and at 12, 24 and 36 hours of reaction times. The experiments in, supercritical CO2 were modelled by using Central Composite Design. The results of polymerisation in SC-CO2 were compared with the results of solution polyrnerization. The yields of Po^din^t%lsuoxane-b-styretieXPDMS-PS) block copolymer obtained was calculated gravimetrieajly an4 its characterisation was determined by FTIR analysis. FUR speptrums mowed that the PDMS-WPS copolymer has the desired structure as expected. The results of ÛPC showed that molecular weight decreased with increasing initiator concentrations and increased with reaction times, whereas yields increased with increasing botii reaction times and initiator concentrations. t6a-DTA results showed that block eopolyiners had decompOsitiqn temperatures higher than polystyrene. Keywords: Supercritical fluids, Polymerization, Polydimethyisiloxane based macroazoinitiator, pory(dimethvlsiloxaperStyrene) block çopolyrhers, sohttkra pplymerizatfcm. x