Effect of time on the hydration and temperature-induced phase separation in aqueous polymer solutions. 1H NMR study

Dehydration during temperature-induced phase separation in D2O solutions of poly(vinyl methyl ether) (PVME), poly(N-isopropylmethacrylamide) (PIPMAm) and poly(N-isopropylacrylamide) (PIPAAm) was followed from time dependences of NMR spin–spin relaxation times T2 of HDO. Both the time characterizing the exclusion of the water from mesoglobules (manifested by the increase in T2 values) and the induction period which precedes the increase in T2 values, increased in the order PVME < PIPMAm < PIPAAm. For D2O solutions of PIPMAm/PVME (or PIPMAm/PIPAAm) mixtures a direct connection between the state of the mesoglobules (hydrated or dehydrated) formed by the component with lower LCST (PVME, PIPAAm) and the temperatures of the phase transition of the PIPMAm component was established by NMR spectroscopy.