Studies On The Nonexponential Relaxation Dynamics Of Binary Molecular Glass Formation Systems

Relaxation is ubiquitous in glass transition and glassy materials.It exhibits obvious dynamic behavior that deviates from exponential in the structural relaxation that dominates the relaxation process.The structural relaxation of the liquid depends on its microscopic basic structural units.The interaction,and the non-exponential nature is the direct reaction of the dynamic coupling strength of these structural units.For multi-component systems,the mixing behavior can effectively improve the ability of forming glass,and the dependence of the glass transition on the components has proved to be of great significance for studying the structural relaxation dynamics of glass-forming mixtures.As a simplest multi-component system,the binary system has attracted extensive attention because of the convenience of adjusting the system interaction by changing the components.Previous research has found that even a small change in the interaction or structure of a system can affect the glass transition process.Although intermolecular interactions are extremely important for understanding non-exponential dynamics,the question of how each component in a mixed system affects the non-exponential relaxation dynamics and what parameters control the width of the relaxation distribution of the dominant mixed system has not been solved.To clarify this issue is of great significance for understanding the effect of interaction forces on the glass transition and for understanding the nature of non-exponential dynamics of structural relaxation.In order to understand the relationship between non-exponential parameters and the heat of mixing during the glass transition,this paper uses differential scanning calorimeters and wideband dielectric spectrometers to measure the structure relaxation of three different binary mixed solutions-ideal mixed solutions with glass forming ability,positive mixed thermal solutions and negative mixing(methyl m-toluate---methyl o-toluate,2-ethyl pyridine---n-ethyl piperidine,1,2-propanediamine---propylene glycol),and the TNMH equation and KWW equation are used to analyze the experimental data.Comparative analysis found that the glass formation systems of three different mixing modes have a strong correlation between mixing enthalpy and non-exponential kinetics.Inenthalpy relaxation,the positive mixed enthalpy system exhibits a narrowing of the relaxation distribution,and the negative mixed enthalpy system broadens the relaxation distribution.Non-exponentiality is more complicated in dielectric relaxation,which is not only affected by the mixing enthalpy,but also has a great dependence on the molecular dipole moment.