Different polymers can be combined into a single material in many ways, which can lead to a wide range of phase behaviors that directly influence the associated physical properties and ultimate applications. Four factors control polymer-polymer phase behavior: choice of monomers, molecular architecture, composition, and molecular size. Current theories and experiments that deal with the equilibrium thermodynamics and non-equilibrium dynamics of polymer mixtures are described in terms of these experimentally accessible parameters. Two representative molecular architectures, binary linear homopolymer mixtures and diblock copolymers, exhibiting macrophase separation and microphase segregation, respectively, are examined in some detail. Although these model systems are fairly well understood, a myriad of mixing scenarios, with both existing and unrealized materials applications, remain unexplored at a fundamental level.

https://science.sciencemag.org/content/sci/251/4996/898.full.pdf

Polymer-polymer phase behavior.

Energy-efficient polymeric gas separation membranes for a sustainable future: A review

This review discusses two classes of organic template-derived amorphous silicas distinguished by the nature of template-matrix interactions and the extent to which subsequent processing dictates the final pore morphology. First we discuss surfactant-templated silicas where the template-matrix interaction is via non-covalent bonding mechanisms and the pore structure is established in the solution stage. We then discuss silicas templated by organic ligands covalently bonded to the siloxane network where subsequent processing strongly influences the final pore structure.

Template-Based Approaches to the Preparation of Amorphous, Nanoporous Silicas

Strategies for compatibilization of polymer blends

The dynamics of concentration fluctuations in binary polymer mixtures AB, A and B being long and flexible chains, is studied near the critical point of unmixing. A ‘‘hydrodynamic’’ theory in close analogy to the treatments of Cahn–Hilliard and Cook for the dynamics of unmixing alloys is developed, and its validity is carefully analyzed. It is shown that homogeneous nucleation for long chains is negligible except in a narrow region of volume fraction φ0 near the spinodal curve φs0 of width (φs0−φ0)/φ0∝N−1, where N is the number of subunits of the chains. For N→∞ the spinodal curve hence is well defined, in contrast to mixtures with short‐range forces, and also the linearized theory of spinodal decomposition is predicted to have wider validity. The collective relaxation in the one‐phase region is described by a characteristic time involving the collective diffusion constant Dcoll τq=(Dcoll q2)−1, if the wave vector q is smaller than the inverse correlation length ξ−1coll, while in the range ξ−1coll≪q≪R−1 (R...

Montgomery T. Shaw

Papers

Polymer-polymer miscibility