Search

Based on a concise review of the experimental data, a theory of the structural, kinetic, and dynamic features of the Fischer cluster is put forward. This theory is based on the idea of heterophase fluctuations of glass-forming liquids. According to these ideas in a one-component liquid the solidlike and fluidlike transient associations of molecules (fluctuons) are formed. The fluctuons differ in the short-range order and, consequently, in the free energy. They form a random free energy landscape. The random field free energy functional of the Ginzburg–Landau type, which accounts for the free energy landscape, is deduced. Based on this, the phase equilibrium, critical behavior, and ordering phenomena of the heterophase liquid are considered. It is shown that in the critical region an effective attractive interaction of the fluctuons results in their gravitation and formation of correlated fractal aggregations. The aggregation consists of the fluctuons of similar short-range order. The fractal aggregation formation is a special structural state of the liquid above the glass transition temperature. The condition at which the aggregations are formed is formulated. Thus it is shown that the Fischer cluster is an array of fractal aggregations of fluctuons. The growth kinetics and dynamics of the Fischer cluster are described. The experimental data are analyzed and discussed using the theory that is put forward. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A microscopic theory based upon the model of molecular defect volume fluctuations is developed to provide an interpretation of the ultraslow mode and excess static light scattering intensity observed in supercooled glass-forming liquids. By including the defect volume as a variable in the set of slow variables comprising of the number density and momentum density, it is shown that in an one component viscoelastic fluid, a diffusive mode associated with the fluctuations of defect volume is present, in addition to the usual q independent structural relaxation mode associated with density fluctuations. Fluctuations of defect volume arise from the configurational rearrangement of molecules. A two fluid model previously proposed for interpreting the anomalous quasielastic light scattering results in an one component fluid follows naturally from the present model. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Correct relations between the dynamic light scattering spectrum and the mechanical creep compliance and longitudinal stress modulus of a viscoelastic liquid are provided. Analysis of the effect of temperature fluctuations on the longitudinal stress modulus is also given. The result provides a basis for determination of mechanical relaxation spectra using the dynamic light scattering technique. [ABSTRACT FROM AUTHOR]

Depolarized Rayleigh spectra of ortho-terphenyl (OTP) were measured in the temperature range from Tg to Tg+190 K. Two samples prepared with and without ‘‘clusters’’ were used for the measurement. Four different Fabry–Perot interferometers covering the time range from about 0.5 ps to 100 ns were employed. Two relaxation modes were observed: a slow mode with all its characteristics of the α process, and a fast mode with a constant, temperature independent relaxation time of about 3 ps. The fast mode has not been reported heretofore. The intensity of the fast mode vanishes at about the Vogel–Fulcher–Tamman temperature T0. The relaxation times of these two processes are found to be identical for both OTP with and without clusters. The temperature dependence of the relaxation time of the α process is Arrhenius at high temperatures, but shows a Williams–Landel–Ferry (WLF) behavior in the range from Tg to Tg+80 K for both samples with and without the long-range density fluctuations (i.e., cluster). [ABSTRACT FROM AUTHOR]