Temperature behavior of thermo-responsive poly-N-vinylcaprolactam and poly-N-isopropylmethacrylamide in aqueous solutions involving organic solutes

Poly-N-vinylcaprolactam (PVCL) and poly-N-isopropylmethacrylamide (PIMA) undergo reversible sharp phase separation in water as a function of temperature. Phase separation behaviour was studied for aqueous solutions of these polymers containing amides and alcohols as a function of solute concentration and structure. It is observed that the temperature behaviour of PIMA is not sensitive to solute structure. For PVCL, solute structure affects the phase separation temperature, and possible reasons for the experimental observations are considered.