STRUCTURE RELAXATION AND METASTABLE STATES AT THE MICROPHASE SEPARATION TRANSITION IN DIBLOCK COPOLYMERS - EXPERIMENTS WITH TIME-RESOLVED SMALL-ANGLE X-RAY-SCATTERING

The kinetics of the microphase separation transition in a diblock copo lymer of polystyrene/polyisoprene was studied with time-resolved small -angle X-ray scattering. Using synchrotron radiation it was possible t o determine the structure factor in time intervals of 10 s. The relaxa tion of the structure factor after temperature jumps within the disord ered regime was found to be wave vector dependent in accordance with C ahn-Hilliard theory. For quenches from the disordered into the ordered state an additional, slow process was found which consists mainly of a decrease in the width of the first-order reflection. It is interpret ed as the perfectioning of the lamellar order. Whereas the correspondi ng relaxation time had been found to decrease strongly with supercooli ng for shallow quenches, it is found to increase again for deeper quen ches.