GAS-CHROMATOGRAPHIC STUDY OF THE INTERACTIONS IN STYRENE-DIMETHYLSILOXANE BLOCK COPOLYMERS AND BLENDS

The biphasic structure of a series of dimethylsiloxane-styrene block copolymers of various composition (22<% PS<84) and molecular weight (2 × 104 < Mn < 11 × 104), obtained by sequential anionic polymerization, has been studied by differential scanning calorimetry, electron microscopy, and small-angle X-ray scattering. The thermodynamics of the interactions between various probes and the block copolymers or the homologous homopolymer mixtures were investigated by gas chromatography either above (120-180 °C) or below (50-80 °C) the PS glass-transition temperature. The experimental data related to the liquid state were taken into account within the framework of the Flory-Huggins theory. It allows the determination of the polymer-polymer interaction parameter as a quantitative measure of the PDMS-PS incompatibility for the block copolymers; it yields the variations of the interaction parameters with temperature, the nature of the probe, and the copolymer composition and molecular weight. A tentative analysis of the interaction between n-decane and the block copolymer in the glassy state yields an estimate of the contribution of the adsorption of the probe at the surface of the PS domains to the total specific retention volumes. Accordingly, it is shown that most of the surface of the PS domains is accessible to the probe. © 1979, American Chemical Society. All rights reserved.