Statistical copolymerization of N-vinyl-pyrrolidone and alkyl methacrylates via RAFT: reactivity ratios and thermal analysis

Abstract

The synthesis of statistical copolymers of N-vinylpyrrolidone (NVP) with the alkyl methacrylates: hexyl methacrylate (HMA) and stearyl methacrylate (SMA), is conducted by reversible addition-fragmentation chain transfer polymerization (RAFT), employing [(O-ethylxanthyl) methyl]benzene and [1-(O-ethylxanthyl) ethyl]benzene as the RAFT agents. The reactivity ratios are estimated using the Fineman-Ross, inverted Fineman-Ross, Kelen-Tudos and Barson-Fenn graphical methods as well as the computer program COPOINT, modified to both the terminal and the penultimate model. In all cases, the NVP reactivity ratio is significantly lower than that of the methacrylates. Structural parameters of the copolymers are obtained by calculating the dyad and triad sequence fractions and the mean sequence length. The thermal properties of the copolymers are studied by Differential Scanning Calorimetry and Thermogravimetric Analysis, and the results are compared with those of the respective homopolymers. In spite of the relatively small amount of NVP in the copolymers, copolymer thermal properties are influenced by both monomers.