Polymer-solvent interactions during phase transition in poly(vinyl methyl ether)/D2O solutions as studied by NMR methods

The structural-dynamic changes and polymer-solvent interactions during temp erature-induced phase transition in poly(vinyl methyl ether) (PVME)/D2O sol utions in a broad range of concentrations (0.1-30 wt.-%) were studied by H- 1 NMR methods. In the whole concentration range the phase transition is man ifested by line broadening (linewidth 350-500 Hz) of a major part of PVME u nits, evidently due to the formation of globular-like structures. Above the LCST transition, the fraction of phase-separated PVME segments is equal to 0.8 +/- 0.1, independent of polymer concentration. While at low concentrat ions the transition is virtually discontinuous, at high concentrations the transition region is similar to 3 K broad. Measurements of nonselective and selective H-1 spin-lattice relaxation times T, of solvent (HDO) molecules evidenced that at elevated temperatures, where most PVME forms globular str uctures, a part of solvent molecules is bound to PVME forming a complex; th e lifetime of the bound water (HDO) molecules is less than or equal to 2 s.