Poly(vinylamine-co-N-isopropylacrylamide) linear polymer and hydrogels with tuned thermoresponsivity†
The fabrication of functional hydrogels with tuned thermoresponsivity is a major challenge. To meet this challenge we copolymerize N-isopropylacrylamide (NIPAm) with N-vinylformamide (NVF) in different ratios with the formamide group being subsequently selectively hydrolyzed to the corresponding amine (VAm). The copolymers are crosslinked with phenylcarbonate telechelic glycol. The influence of the NIPAm : VAm ratio on the thermoresponsitiviy is investigated in terms of absorbance, rheology, NMR spectroscopy, relaxometry, and diffusometry. Phase transition temperatures, change in the entropy of the polymer–water system, and width of the transition in the process of coil-to-globule and swollen-to-collapsed network transitions were evaluated by a two state model and Boltzmann sigmoidal function.