A deeper insight into the dual temperature- and pH-responsiveness of poly(vinylamine)-b-poly(N-isopropylacrylamide) double hydrophilic block copolymers

Block copolymers based on poly(vinylamine) and poly(N-isopropylacrylamide), PVAmm-b-PNIPAMn, were synthetized by hydrazinolysis of poly(N-vinylphthalimide) based copolymers, PVPIm-b-PNIPAMn, obtained by RAFT polymerization. The effect of molar mass and pH on the thermoresponsive and aggregation properties of these polymers in aqueous solution was studied with UV–vis spectroscopy, differential scanning calorimetry, NMR spectrometry, light and X-ray scattering experiments. For the first time it was demonstrated that at room temperature, these copolymers are prone to self-assemble and tend to form larger aggregates upon heating. Hence core-shell nanostructures with a dense PNIPAM core and a hydrophilic PVAm shell, were notably observed above Tc when pH < pKa.