Unified Approach to Ion Transport and Structural Relaxation in Amorphous Polymers and Glasses

• Published in: The journal of physical chemistry. B Vol. 112; no. 3; pp. 859 - 866
• Main Authors: Ingram, Malcolm D, Imrie, Corrie T, Ledru, Jacques, Hutchinson, John M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.01.2008
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp0754482

Kinetic data for structural relaxation in silver iodomolybdates at the glass transition temperature (T g) are obtained by high-pressure differential scanning calorimetry (HP-DSC) and are compared with activation energies (E A) and volumes (V A) obtained earlier from conductivities below T g. The results are fitted to an empirical equation, E A = MV A, and displayed in the form of a master plot of E A versus V A, an approach previously applied to strongly coupled systems, including polymer electrolytes and molten salts above their glass transition temperatures. The parameter M emerges as a localized modulus, expressive of interatomic forces within the medium, linking together E A, σ, V A, σ and E A,s, V A,s, the “apparent” activation parameters for ionic conductivity and structural relaxation, respectively. The V A and E A values for ion transport are much smaller than the corresponding values for structural relaxation. However, remarkably close agreement emerges between the “process parameters”, M s and M σ, both close to 8 GPa, thus establishing a quantitative link between ion transport and structural relaxation in this highly decoupled system. A new E A versus V A master plot is constructed, which points the way to a unified approach to ion transport in polymers and glasses.