Multi-responsiveness N-vinylpyrrolidone and methyl acrylate copolymer with wide tunable range of response temperature

Copolymers of N-vinylpyrrolidone (NVP) and methyl acrylate (MA) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization, which exhibited typical lower critical solution temperature (LCST) behavior in aqueous solution. The molecular structure and composition of copolymer P(NVP-co-MA) were characterized by FTIR and NMR. The response behavior was investigated by UV transmittance tests. The LCST of the copolymer P(NVP-co-MA) can vary from 17 °C to 90 °C by adjusting the ratio of the two monomers, showing a wide tunable range. The dynamic light scattering (DLS) results showed that beyond LCST, the hydrodynamic size increased with increasing temperature, polymer molecular chains aggregated in solution, and solubility deteriorated, confirming its LCST responsiveness. In addition, the copolymer P(NVP-co-MA) is salt responsive as well as pH-responsive. The multi-responsive and biocompatible copolymer has a large potential application in the fields of materials and biomedicine.