THE EFFECT OF CHARGED IMPURITIES ON A GLASS TRANSITION IN A POLAR MEDIUM

摘要

A phase transition from a liquid to glass state is studied for polar solvents in the presence of ions. The entropy and free energy of the system above and below the transition temperature, T-c, is found on the basis of the theory of random dipole-dipole and charge-dipole interactions. The dependence of the transition temperature on the concentration of charged impurities, c, is found. It is shown that a relative charge concentration of only 10(-5) is needed to increase T-c by 20 K. The transition temperature is also dependent on the value of the charge. For a Fe+3/Fe+2 reactive complex the transition temperature is changed by 10 K for c = 10(-6). For dissolved salts we describe the relationship between T-c and the separation distance of the ion pair. The glass transition is insensitive to the size of dissolved ions. The theory proposed has only one adjustable parameter, the elementary dipole moment of the solvent. The theory allows to explain a peak dependence in T-c measured as a function of the alcohol content Y in Li+Cl-. 5H(2)O . Y alcohol(methanol, ethanol, 1-propanol) mixtures. (C) 1996 American Institute of Physics. [References: 24]