1H NMR study of thermotropic phase transition of linear and crosslinked poly(vinyl methyl ether) in D2O

The changes in the dynamic structure during temperature-induced phase transition in poly(vinyl methyl ether) (PVME)/D2O solutions and gels in a broad range of concentrations (c=0.1–30 wt%) and crosslinking densities, respectively, were studied by 1H NMR methods. Similar behaviour was found both for linear and crosslinked systems, indicating the formation of compact globular-like structures during the phase transition. The fraction of PVME segments in globular-like structures is ∼0.85 for solutions and ∼1.0 for swollen networks, independent of the polymer concentration or the crosslinking density. While for dilute PVME solutions the thermotropic transition as detected by NMR is virtually discontinuous, for semidilute and concentrated solutions, and for swollen networks, the transition sets in at lower temperatures and its width is several Kelvin broad.