Order parameter relaxation theory

The order parameter relaxation near the critical point is quantitatively described by the mode-mode coupling theory (Kawasaki, 1966, 1970ab Kadanoff and Swift, 1968 Kawasaki and Lo, 1972 Lo and Kawasaki, 1972 Swinney, 1974 Anisimov, 1987). 

They can serve therefore as a test for Ti dispersion. In Fig. 12 the relaxation results are shown for D-RADP-15. The solid lines are a fit of the theory [19] to the data. Above Tc the lit is excellent, whereas below Tc it probably suffers from the fact that the phase transition is already diffuse and only nearly of second order. This proves that a soft mode component is needed to explain the data. Furthermore, the fact that the ratio ti/t2 remains unchanged above and below Tc proves that the order parameter fluctuations are in the fast motion regime on both sides of the transition. 

As has been discussed by Hsich [12, 13], any chemical relaxation (reaction) or structural relaxation can be explained from irreversible thermodynamic fluctuation theory in which changes of physical and mechanical properties during the relaxation process can be interpreted and predicted from the mean square fluctuations of thermodynamic ordering parameters. Then the physical or mechanical properties at any given cure time can be written as a relaxation function ... 

The LdG theory can be used to develop a macroscopic description of the dynamics of the pseudonematic domains in terms of the rate equations for the order parameters Qap [2]. An exponential relaxation for Qyp is then obtained with a rate... 

In particular, the expressions obtained for. the segmental order parameters S and the effective relaxation rates k provide a molecular justification of the model-free parameters used to analyze NMR relaxation experiments. The theory also supplies detailed interpretation of the... 

---