Spinodal decomposition of a symmetric critical mixture of deuterated and protonated polymer

Abstract

A nearly symmetric critical mixture (φc=0.486) of perdeuterated and protonated 1,4-polybutadiene exhibiting an upper critical solution temperature Tc=61.5±1.5 °C has been quenched from the homogeneous state (≂75 °C) to various temperatures between 25 and 57.5 °C. Light scattering measurements document the subsequent spinodal decomposition process which we describe based on a four-stage model: early, intermediate, transition, and final. The early stage is accounted for by the Cahn theory, yielding initial correlation lengths and effective diffusion coefficients in quantitative agreement with mean-field predictions. Nonlinear effects mark the beginning of the intermediate stage, which exhibits a simple power-law growth of heterogeneity length Lm(t)∼tneff, but with a temperature dependent exponent neff. As the composition fluctuation amplitude approaches the equilibrium values, the spinodal decomposition process enters the transition stage, characterized by a decreasing interfacial thickness and an increasing Lm(t). Once the interfacial profile equilibrates, a crossover to the final stage occurs. Subsequent growth of L(t) leaves the morphology unaffected as evidenced by a universal structure factor. These findings are discussed in the context of the current theory and are compared with prior studies involving polymer–polymer and simple liquid mixtures.

The interface in demixed colloid–polymer systems: wetting, waves and droplets

“…In fact, only in a few systems the linear Cahn-Hilliard regime has been observed, e.g. in polymer-polymer systems [231][232][233], and the crossover between the diffusive and the viscous regime has been observed for example in [234,235] for binary fluid mixtures.…”

Fluid-fluid phase separation in colloid-polymer mixtures studied with small angle light scattering and light microscopy

“…Although experimentally we detected a scattering ring with a continuously decreasing radius (Fig. 3), we attempted like other authors [26], to find a linear Cahn-regime in the initial stage of phase separation. Fig.…”

“…In order to analyse the phase separation kinetics in our colloid polymer mixtures we compared our results with theories developed for liquid-liquid phase separation, that have already been applied in a wide range of dissimilar systems such as binary liquid mixtures [22,23], metallic alloys and inorganic glasses [24,25], polymer blends and mixtures [26,27], micelles [28] and thermodynamically unstable colloidal systems [29,30]. Following Cahn [25,[31][32][33][34] it has become customary to distinguish between two kinds of mechanism which describe the early stage dynamics of phase separation: spinodal decomposition in thermodynamically unstable systems versus nucleation and growth in thermodynamically metastable systems.…”

Thermodynamics and Phase Behavior of Block Copolymer/Homopolymer Blends with Attractive and Repulsive Interactions

“…This has been exploited in studies of binary homopolymer blends, block copolymer melts, and mixtures thereof. [2][3][4][5][6][7][8][9][10][31][32][33][34][35][36][37] The purpose of this paper is to study both pretransitional concentration fluctuations and phase behavior in A-B/C mixtures with both attractive and repulsive interactions. The specific system studied in this paper is a blend of poly-(ethylene-block-head-to-head propylene) copolymer (PE-PP) and a polyisobutylene homopolymer (PIB).…”

“…[1][2][3][4][5][6][7][8][9][10] Predicting the thermodynamic properties of individual chains requires knowledge of two parameters: the statistical segment length, l, which accounts for local intrachain correlations on the monomer length scale, and the chain length, N (number of monomers per chain), which characterizes the large length scale properties of the chains. The interactions between different chains are characterized by a Flory-Huggins interaction parameter, .…”