RELAXATION OF ELECTRIC BIREFRINGENCE NEAR A CRITICAL CONSOLUTE POINT

An experimental investigation of the relaxation of electric birefringe nce in the critical binary mixture n-butylbenzene-propylene carbonate is presented. The decay functions observed at different temperatures i n the critical region are clearly nonexponential and show a scaling be havior. The experimental relaxation function is compared with theoreti cal predictions: the asymptotic decay is a stretched exponential with a stretch exponent 0.40 +/- 0.03, in good agreement with the dynamic d roplet model, but the earlier stages are very well described also by t he Onuki-Doi approach [Europhys. Lett. 17, 63 (1992)].