Molecular director axis polymer orientation

As for the chain backbone, the PMA6,4 polymethacrylate has been studied in the frozen smectic phase. The preferential orientation of the C-C H3 bonds at 54° with respect to the director is only consistent with an orientation of the chain perpendicular to it. The width of the orientational distribution of the C-CH3 bonds with respect to the director has been determined to be only 20°, which indicates the high conformational order at this site. However, lineshapes obtained from the two deuterated sites of the main chain cannot be interpreted in terms of an 3 l-trans conformation of the chain backbone. The link between the polymer chain and the mesogens is provided by the conformationally ordered quaternary carbon in the polymer chain. Molecular order of the main chain has also been investigated for PA6 1 and PMA6 As for PMAe,4, PMA6,i polymethacrylate in its frozen nematic phase has a main chain which is oriented perpendicular to the director. By contrast, in the frozen smectic phase of the polyacrylate the chain is found to be oriented parallel to the director. These results are consistent with the molecular shape of the polymer as a rotational ellipsoid with its long axis parallel to the director for the polyacrylate and perpendicular to the... 

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