Conductance and relaxations in the glassy and rubber states of aqueous poly( vinyl pyrrolidone): A cryofixation medium

Abstract

AbstractThe dielectric permittivity and loss of poly(vinyl pyrrolidone), molecular weight 40,000, containing 40% (by weight) water have been measured over the temperature range 77–325 K and frequency range 12 Hz to 0.1 MHz. A prominent relaxation due to rotational diffusion of water molecules in a hydrogen‐bonded structure occurs at T < Tg (237 K). The half‐width of the dipolar relaxation spectra is 2.27 decades and is temperature independent, which is strikingly different from the corresponding features of pure polymers. It is concluded that H‐bonded amorphous solid water persists in the glassy polymer matrix and that the H‐bonded structure contains the pyrrolidone side groups of the randomly oriented chain. The relaxation peak at T near Tg is masked by a large dc conductivity which, when expressed in terms of electric modulus, has a spectrum of half‐width 1.37 instead of 1.14 decades expected for dc conductivity alone. The contribution from dipolar reorientation in the glass‐rubber range of the PVP‐H2O solution is smaller than that in its sub‐Tg relaxation.