The kinetics of dithiocarbamate-mediated polyurethane-block-poly(methyl methacrylate) polymers

Abstract

One important advantage offered by polymeric iniferters is the possibility that polycondensation polymers could be further reacted with vinyl monomers to produce novel block copolymers with interesting properties. The objective of this work was the kinetic investigation of polyurethane-block-poly(methyl methacrylate) (PU-b-PMMA) using dithiocarbamate (DC)-based polyurethane macroiniferter (PUMI) at different concentrations. It is shown that the copolymerization reactions followed the first order dependency. A linear increase of molecular weight with monomer conversion demonstrated that the copolymerization followed the mechanism of controlled radical polymerization. The rate of polymerization (Rp) at specific reaction time increased as the PUMI concentration increased from 0.34 × 10−3 mol/L to 2.74 × 10−3 mol/L, pass through a maxima, and decreased as PUMI concentration was increased beyond 2.74 × 10−3 mol/L. The thermogravimetric analysis showed that both PUMI and PU-b-PMMA degraded in three distinctive stages but the PU-b-PMMA is thermally more stable than the PUMI especially at lower temperatures. Thus, a combination of polycondensation and free radical photopolymerization methods, as demonstrated in this study, could be used to synthesize polyurethane-based block copolymers with tailored chain lengths of different blocks suitable for biomedical applications.