1H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

H-1 NMR spectroscopy was used to investigate thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide) (PIPMAm)/poly(vinyl methyl ether) (PVME) mixtures. In all studied solutions (polymer concentrations c=0.1-10wt%) two phase transitions were detected at temperatures roughly corresponding to different lower critical solution temperatures of PIPMAm and PVME. While the phase transition of PVME component (located at lower temperatures) is not affected by the presence of PIPMAm in the mixture, the phase transition temperatures of PIPMAm component (located at higher temperatures) are affected by the phase separation of the PVME component. Measurements of H-1 spin-spin relaxation of residual water (HDO) molecules revealed that above the phase transition, a certain portion of water molecules is bound to polymer globular structures. A major part of bound water is present in globular structures of predominating polymer component in the mixture. (C) 2004 Elsevier Ltd. All rights reserved.