Synthesis and characterization of polyvinyl alcohol-g-polystyrene copolymers via MADIX polymerization technique

In polymer structure design, branching can occur randomly or by reactions designed to target specific architectures. This microstructural property affects many physical properties such as polydispersity, molecular weight and polymer chain size. A new reversible addition-fragmentation chain transfer/macromolecular design through interchange of xanthates (RAFT/MADIX) agents with polyvinyl alcohol was performed. In the process, polyvinyl alcohol (PVA), potassium hydroxide, carbon disulfide and derivatives of benzoylchloride were employed, and thus, three new graft chain transfer agents (g-CTA) were synthesized. PVA-g-PS graft copolymers were obtained using MADIX agents by changing various factors including initiator, amount of monomer and reaction time. While the linear increase in molecular weight with monomer consumption was observed, the polymerization reaction was kinetically detected to be the first order. Significant progress has been made in controlling the molecular weight distribution of the polymer by RAFT polymerization. The synthesized graft copolymers were characterized using FTIR, H-1 NMR, C-13 NMR, GPC and DSC techniques. Also, the three new graft chain transfer agents were characterized by elemental analysis and the existence of xanthate -S-(C = S) O-PVA was confirmed. The synthesis of the copolymer with the MADIX agent, which has an almost infinite number of design possibilities, was successfully achieved. As a result, well-defined statistical PVA-g-PS copolymers having a narrow molecular weight distribution (PDI 1.23-1.47) were obtained.