Abstract
The disorder-to-order transition in a series of asymmetric diblock copolymers of polystyrene/polyisoprene is studied using small angle X-ray scattering. In between the homogeneously disordered state at high temperature and the b.c.c. ordered array of spheres we find a stable state of liquid-like order between the spherical domains. Quantitative analysis of this order is possible in the framework of the Percus-Yevick theory for hard sphere liquids. The transition to the ordered state occurs at a sphere volume fraction of 0.47. The analysis of the scattering from the ordered state involves both the Bragg scattering and the strong diffuse scattering component. The size of the spheres may thus be determined in the disordered and in the ordered state and is found to increase continuously with decreasing temperature. Time resolved scattering after temperature jumps from the disordered into the ordered state reveal the existence of well separated timescales on which structure formation proceeds. They are identified as the increase of sphere size and their subsequent arrangement on the b.c.c. lattice.
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