Reverse iodine transfer copolymerization of styrene and acrylonitrile: copolymer synthesis, characterization and kinetic study

Random copolymers of poly (styrene-co-acrylonitrile) (SAN) via reverse iodine transfer copolymerization of styrene (St) and acrylonitrile (AN) were synthesized using carboxyl functional initiator 4, 4ʹ-azobis (4-cyanovaleric acid) (ACVA) and molecular iodine (I₂) at 80 ℃^. The characterization of resultant random copolymer via FT-IR, ¹H-NMR, GPC, and DSC analysis confirmed that well-defined SAN copolymers with different copolymer compositions of acrylonitrile \({(\stackrel{-}{\mathrm{F}}}_{\mathrm{AN}}=0.23-0.46)\) and monocarboxylic acid functionality, were synthesized. The kinetics results showed that the copolymerization rate obeyed the first-order kinetics model with respect to the monomer concentration, a linear increase of the molecular weight with increasing monomer conversion and a relatively low dispersity index (Ɖ ~ 1.4) was observed. The reactivity ratios of the St and AN were calculated using the extended Kelen-Tüdos (K-T) method to be \({\mathrm{r}}_{\mathrm{St}}=0.431\pm 0.0406\mathrm{ and }{\mathrm{r}}_{\mathrm{AN}}=0.224\pm 0.0164\), respectively. Finally, the Barton model generated a satisfactory fit to the experimental data of the copolymers’ glass transition temperatures.