Orientation analysis of polyacetylene with liquid crystalline side chains

Article abstract of DOI:10.1016/S0022-2860(97)00297-4

Polyacetylene substituted by liquid crystalline side chains and its monomer were characterized by ¹³C NMR spectroscopy in order to investigate their orientation and dynamics in the liquid crystalline state. Anisotropic chemical shifts of phenylene carbons, acetylene carbons and ethylene carbons were analysed. In both the monomer and the polymer, phenylene carbons showed downfield chemical shifts indicating their orientation to the magnetic field. On the other hand, by comparing observed chemical shifts and theoretical ones, acetylene carbons in the monomer were found to move freely in the liquid crystalline state. For the polymer, the dynamics of ethylene carbons (polyacetylene backbones) was interpreted in terms of a swing model, while that of side-chain phenylene carbons was explained as a swing model synchronized with the main chain accompanied by rotation around the director. These results directly revel the scheme of the alignment of the main chain induced by the side chain orientation, and also suggest that the polymer structure is constructed by head-to-head or tail-to-tail type connection of monomers.