They propose a scheme to construct and characterize the structure and properties of polymer grain boundaries in a controlled manner. The essential idea is to carefully and systematically establish the influence of well-defined, specific grain boundary defects on the physical properties of polymers. Conventionally processed crystalline polymers have small crystallites (10-20 nm), which implies a large defect density in the solid state. Although this means that structural defects play an important or even dominant role in polymer systems, it also makes it difficult to isolate the effect of a particular devect on a macroscopically observed property. However, the development of solid-state and thin-film polymerization mechanisms have facilitated the synthesis of highly organized and ordered polymers. These systems provide a unique opportunity to isolate and investigate in detail the structure of covalently bonded solids near defects and the effect of these defects on the properties of the material. They will examine structure-property relationships in poly(diacetylene) thin films and crystals. They describe procedures for growing crystals of diacetylene monomers, joining these together to make a grain boundary, and then polymerizing through the grain boundary by exposure to Co60 radiation. With this approach it will be possible to prepare "polymer bicrystals". A simple scheme for measuring the photoconductive response of these bicrystals will be used, a transport property which should depend on the structure of the boundary. Structural characterization involving X-ray scattering and Transmission Electron Microscopy (TEM) will be also carried out.
