Polymer and organic molecules ordered via epitaxy: Geometrical and molecular interactions

Control of structural order at the molecular level for both conventional li near polymers and conjugated polymers with valuable optoelectronic properti es has major consequence on the macroscopic properties of these polymers. T hough the traditional means of orientation of polymer was mechanical deform ation, presently extensive works are concerned with a more controlled way o f orientation: epitaxial crystallisation. Most of the first. documented exa mples of epitaxial growth of conventional polymers on single crystals follo wed the well-established geometrical rules of best matching. However, recen t examples show off more subtle rules of selection. Analogous cases, follow ing or breaking the matching rules, have been observed for diacetylenes ord ered via epipolymerisation on single crystals. Hereafter, representative ex amples of the structural matching rules are depicted first, and then recent examples, which depart from the simple geometrical fitting, are described. The analysis of the former leads to define the subtle matching rules apply ing for polymers linked to their conformational adaptability. The analysis of the latter gives the opportunity to discuss the relative influence of ge ometrical and molecular interactions between the deposit and the substrate.