Regulation of the thermal sensitivity of hydroxypropyl cellulose by poly(N-isopropylacryamide) side chains

Hydroxyproyl cellulose graft poly(N-isopropylacryamide) (HPC-g-PNIPAm) copolymers were synthesized by single-electron transfer living radical polymerization (SET-LRP) in water and THF mixture solvent and characterized. The controllability and polymerization rate of SET-LRP can be adjusted by the water/THF ratio in the mixture solvent. The monomer conversion rate is relatively low in the solvent with low water content. The thermal responsive property of HPC-g-PNIPAm copolymers in aqueous solution depends on the length of the graft chains. The relatively short PNIPAm side chains (<150 repeat units) can effectively regulate the low critical solution temperature (LCST) of the HPC-g-PNIPAm copolymers in aqueous solution due to the hydrophilic properties of the short PNIPAm chains. This work provides an approach for the regulation of the LCST to body temperature region by graft copolymerization.