Abstract
Atom transfer radical polymerization of vinyl pivalate was carried out in supercritical carbon dioxide using CuBr or CuCl/terpyridine (tpy) complex system and ethyl 2-bromoisobutyrate as an initiator. The reaction kinetics of the two different catalytic systems (CuBr/tpy and CuCl/tpy) was investigated. In addition, the effects of temperature, pressure, and catalyst/ligand concentration were examined systematically to obtain an acceptable rate of polymerization and control over the number-average molecular weight (Mn) and polydispersity index (PDI). The result showed that relatively low PDIs were obtained and polymerization rates were enhanced at higher pressures. The CuCl/tpy complex exhibited the maximum conversion of 90% with a Mn and PDI of 60.2kg/mol and 1.29, respectively. The CuCl/tpy catalyst system showed better agreement between theoretical and experimental Mn compared to the CuBr/tpy. The living character of poly(vinyl pivalate) (PVPi) was proven by 1H NMR spectrum and chain extension reaction. The formation of poly(vinyl alcohol) via saponification of the resulting PVPi was also carried out. The structures of both PVPi and PVA were examined by 1H NMR and FTIR spectra.
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