| Abstract
| - The local ordering, morphology, and dynamics of aromatic cores and flexible alkyl spacerswere analyzed for a homologous series of main-chain polymeric liquid crystals. 13C NMR experimentsshowed that the nematic ordering achieved by these synthetic polymers was retained into the solid stateif their quenchings occur while remaining within the strong NMR magnetic field. The degree of orientationin the resulting glasses was investigated by variable-angle NMR experiments and found to differ betweenpolymers with an even number of methylene units in the flexible spacer vs those with an odd number.To further discern at a molecular level the nature of these differences, the structures of these polyesterswere examined by high-resolution solid-state 13C NMR. It was found that while the odd-chained seriesdisplayed a conformational annealing upon aligning, even-chained polymers were generally in all-transconformations both for as-synthesized and for aligned samples. Variable-temperature 1D and 2D NMRexperiments also illustrated substantial differences in the degree of motional dynamics between the oddand even polymer series: whereas considerable rigidity was exhibited by the even-numbered series allthe way up to 150 °C, a relatively high flexibility displayed by the odd-methylene polymers. In unison,these measurements provide insight into the significant changes that can be imparted into the structureand dynamics of main-chain thermotropic polymers by subtle manipulations of their monomeric structures.
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