Static and dynamic scattering at the microphase separation transition in block copolymers

Abstract

A series of polystyrene/(cis 1–4)polyisoprene diblock copolymers is studied using small-angle x-ray scattering (SAXS), real-time SAXS, photon correlation spectroscopy (PCS) and dielectric spectroscopy (DS). The static structure of concentration fluctuations is found to deviate from the Gaussian coil assumption in a temperature regime above the microphase separation transition (MST). The dynamic experiments in this temperature regime test concentration fluctuations (real-time SAXS) as well as single-block dynamics (PCS and DS) making use of the intrinsic labelling properties of this specific diblock copolymer. They provide evidence for the existence of partially ordered domains above the MST. The assumption of a weakly segregated state is, therefore, questionable.