An important trend in thermoplastics is the growth of products based on polymer-polymer blends. They are called "engineered" thermoplastics because they have high enough modulus, toughness and softening temperature to be used the same way metals are used. Most of these blends are immiscible but stabilized in a highly dispersed morphology by graft or block copolymers at the interface between the phases. One way to make these copolymers is by coupling reactions during melt blending. This research will focus on blends of two immiscible polymers, one rigid (glass transition temperature greater than ambient temperature) the other soft (glass transition temperature less than ambient temperature). Initially both phases will be amorphous. The strategy will be to design several model reactive polymer pairs and combine them in a small laboratory melt mixer which duplicates the essential features of the industrial scale process. The PIs plan to identify the major variables controlling the process by changes in composition, chemistry, polymer architecture and chain length. Scanning and transmission electron microscopy will be used as the major microstructural characterization method. From image analysis on these micrographs and single drop studies, the drop break up and coalescence process with interfacial reaction will be modeled. This research should yield better methods for the analysis of these polymer blends as well as a fundamental understanding of the process and new blend compatibilizing methods and materials.
