Homogeneous Polymer Blends from Immiscible Polymer Mixtures by Entropy Diluent

Abstract

The miscible polymer blend is challenging from a thermodynamic perspective. Various methods have been attempted to overcome the difficulty of making miscible polymers, especially in the absence of specific interactions. In this study, we demonstrate a straightforward preparation method for homogeneous polymer blends from polymer mixtures that were previously considered immiscible. This is achieved by reducing the conformational entropy of polymers using an entropy diluent. The model system used in this demonstration involves polystyrene (PS) and poly (methyl methacrylate) (PMMA). The entropy diluent, benzoic acid (BA), induces spontaneous extension of PS and PMMA chains through hydrogen bonding. The resulting PS/PMMA blend (PS/PMMABA) exhibits structural heterogeneity at several tens of nanometer scale, but no visible phase separation is observed through optical microscopy (OM) and scanning electron microscopy (SEM). Moreover, PS/PMMABA demonstrates a single glass transition temperature (Tg), providing strong evidence of homogeneity. Additionally, the mechanical property (E') is significantly improved compared to that of each homopolymer.