Nitroxide-Mediated Polymerization of Vinyl Chloride at Low Temperature: Kinetic and Computational Studies

The synthesis of poly(vinyl chloride) (PVC) by nitroxide-mediated polymerization (NMP) using the SG1-based BlocBuilder alkoxyamine at low temperature (30 and 42 degrees C) is reported. The reaction system was studied regarding the nature of the solvent, the monomer-to-solvent ratio, the polymerization temperature, and the target molecular weight. First-order kinetics and linear evolutions of the molecular weight with vinyl chloride (VC) conversion were obtained in dichloromethane (DCM) and dimethyl sulfoxide (DMSO) together with decreasing dispersities ((D) over bar) down to 1.59-1.47. The resulting PVC was fully characterized by H-1 nuclear magnetic resonance spectroscopy (H-1 NMR), P-31 NMR, and size exclusion chromatography (SEC). The H-1 NMR and P-31 NMR revealed the existence of very small content of structural defects and the presence of chain-end functional groups (similar to 91% SG1 chain-end functionality). Chain extension experiments were performed with VC, methyl methacrylate (MMA), and a mixture of monomers (90% of MMA and 10% of styrene (S)) and confirmed the "livingness" of the PVC-SG1 macroinitiators, giving access to different PVC-based block copolymers. High level ab initio molecular orbital calculations suggested that the C-O bond in the PVC-SG1 alkoxyamine is too strong to mediate the NMP of VC by simple "classic" activation-deactivation equilibrium and is possibly being mediated by a SG1-mediated dehydrochlorination mechanism. The results presented in this study established a new route to afford a wide range of new complex macrostructures based on PVC segments.