Diblock copolymers interfacial interaction between blend phases

One possible way of reducing interfacial tension and improving phase adhesion between PP-based blend phases is to use a selected copolymeric additive that has similar components to the blend, as a compatibilizer in the blend system. Well-chosen diblock copolymers, widely used as compatibilizing agents in PP-based blends, usually enhance interfacial interaction between phases of blends (15, 16), reduce the particle dimensions of the dispersed phase (16, 17), and stabilize phase dispersion against coalescence (16-18) through an emulsification effect, thus improving the mechanical properties (15-19). 

There can be two definitions of the term compatibilization . The first is the process of reinforcement of the interfacial border in an immiscible polymer blend. The physical essence consists of increasing the interaction between two phases by introduction of substances like diblock polymers, when dissimilar blocks of copolymer will locate at the phase interface. Such com-patibilizers do not change the thermodynamic stability of the system and at the same time vary the morphology of the composition, leading to a more fine dispersion of components in the course of blending. 

In more recent work by Shull and coworkers, the preparation of swollen micelle composites was investigated using self-consistent mean theory (Lefebvre and Shull, 2006). This theoretical approach concluded that nanoparticles can be encapsulated in the center of swollen micelles by including an external-field term that creates an attraction between the surface of the particle and the homopolymer. This predicts the formation of nanocomposites from a diblock copolymer (AB) and additional selectively attractive homopolymer (C). This is achieved by first preparing a layer of C homopolymer, then a layer of nanoparticles, and then a blend of A homopolymer and asymmetric AB copolymer. Then upon annealing, favorable interactions between B and C repeat units cause the copolymer to migrate to the A/C interface. Attraction between the particle and the C repeat units causes the particles to diffuse into the C phase. When the interfacial tension is lowered by the copolymer, the interface develops curvature and micelles swollen with C form around the particles in the A phase. 

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