Author/Authors :
M. Pastorczak، نويسنده , , Marcin and Wübbenhorst، نويسنده , , Michael and Dominguez-Espinosa، نويسنده , , Gustavo and Okrasa، نويسنده , , Lidia and Pyda، نويسنده , , Marek and Kozanecki، نويسنده , , Marcin and Kadlubowski، نويسنده , , Slawomir and Ulanski، نويسنده , , Piotr and Rosiak، نويسنده , , Janusz M. and Ulanski، نويسنده , , Jacek، نويسنده ,
Abstract :
The phase transition observed by various methods in poly(vinyl methyl ether)/water systems at around 18 °C has been assigned by some investigators to the pre-melting of water and by others to a glass transition of the polymer. In this study, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry were used to identify this transition in radiationally crosslinked poly(vinyl methyl ether) hydrogels, as well as to analyse sub-zero relaxation processes in such a three-phase (polymer/ice/liquid water) system. The process at 18 °C was related to the pre-melting of water induced by the segmental motions of the polymer; however, it was seen to be one transition due to the cooperative motions of both compounds. The atypical (two regimes) temperature dependence of the segmental motion process was observed and was related to confinement of the polymer chains between ice clusters below approximately −24 °C; furthermore, the main dielectric process of hexagonal ice was identified and a Maxwell-Wagner effect was observed.
