Molecular Assemblies in Multicomponent Linear Chain Solids

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To characterize the solid state molecular interactions within binary and multicomponent polymethylene chain arrays, electron diffraction data from oriented single microcrystals will be employed to elucidate their crystal structures. This will provide a unique opportunity to uncover information (e.g. packing symmetry, unit cell dimensions, co-existence of similar crystalline polymorphs or alternate crystal structures, accommodation of non-overlap molecular volumes) previously hidden to powder diffraction investigations due to reflection overlap. Techniques developed in this laboratory will provide reliable intensity data from the most informative projections of the unit cell, in order to carry out quantitative direct structure analyses. Low dose electron microscopic lattice imaging will also depict interfaces at phase boundaries. Factors influencing the stabilization of solid solutions (chain length differences and length distribution, heterogroup and branch inclusions) will be studied, both for stable lamellae as well as incompletely separated lamellae that include long 'bridging molecules'. The progress of phase separation for two- and three-component metastable solid solutions within a miscibility gap will be characterized by electron crystallography to define the crystal packing of the final solids, in order to discern common features that would suggest a diffusion path. Crystallographic characterizations of eutectic solids will identify interfacial interactions across phase boundaries, testing the general occurrence of epitaxial interactions between these contacting domains.%%%The molecular and structural characterization of these polymeric materials is important in understanding and optimizing their properties. ***