Effect of copolymer composition of RAFT/MADIX-derived N-vinylcaprolactam/N-vinylpyrrolidone statistical copolymers on their thermoresponsive behavior and hydrogel properties

Abstract

Thermoresponsive statistical copolymers of N-vinylcaprolactam and N-vinylpyrrolidone of controlled average molar masses and composition were synthesized by RAFT/MADIX polymerization. The cloud point temperature was finely tuned in the range of temperature 36–70 °C. DSC measurements combined with statistical calculations suggest that the whole polymer chain is involved in the hydration/dehydration process rather than short polymer sequences. At high concentration, these polymers enable the formation of thermoresponsive hydrogels. Cryo-SEM analysis of these solutions showed the presence of globular substructures, with a looser 3-D network at higher VP content. This decrease of density of entanglements in the gel network could explain the decrease of mechanical properties and faster rehydration kinetics of the thermogelling polymer.