S. Chvalun, J. Blackwell, J. Cho
Sep 1, 1998
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0
Influential Citations
26
Citations
Journal
Polymer
Abstract
Abstract Small angle and wide angle X-ray methods have been used to study the structure 2-{2-(2-hydroxyethoxy)-ethoxy}ethyl-3,4,5-tris( p -octadecyl-oxybenzyloxy)-benzoate (H18-ABG-3EO-OH), which is one of a series of precursors used to synthesize polymers with highly tapered side chains that form self-assembling, columnar hexagonal ( φ h ) phases. This material is crystalline at room temperature, and undergoes crystalline-to- φ h and φ h -to-isotropic transitions in the region of 65–70 and 75–80°C respectively, depending on the thermal history. Small angle X-ray data for oriented fibres drawn from the φ h phase and cooled to room temperature point to the presence of hexagonally packed columns with a diameter of 57 A. The corresponding wide angle data indicate that there is three dimensional order within the columns: we observe a six-point pattern probably due to packing of the C18 tails in a manner analogous to the hexagonal form of polyethylene. On annealing, there is a progressive increase in the internal order of the cylinders as the structure is converted to one analogous to the crystalline forms of the C12-tetraethoxy analog (H12-ABG-4EO-OH) and the methacrylate polymer thereof (H12-ABG-4EO-PMA). These results suggest that the internal ordering now extends to the aromatic and tri-ethoxy units. Heating and cooling cycles from room temperature to successively higher temperatures show that these improvements in the internal order are accompanied by a progressive reduction in the diameter of the cylinders.