| New disubstituted polyacetylenes carrying functional groups (FG) -{lcub}(R)C=C[(CH 2)m-FG]{rcub}p-, -[(R)C=C(C6H4-FG)]p-, and -[(R)C=C(CO2-FG)]p- (R = CH3, n-C6H13, C6 H5) were designed and synthesized. The monomers were prepared in high yields by multi-step reactions. Polymerizations of the monomers were effected by inexpensive classical metathesis catalysts of MoCl5-, WCl6-, NbCl5-, and TaCl5-Ph4Sn, giving high molecular weight polymers in high yields (M w up to 8.7 × 105 Da and isolation yield up to 99%). The structures and properties of the polymers were well characterized and evaluated by IR, NMR, UV, TGA, PL, EL, DSC, POM, XRD, SEM, and CD analyses. All the polymers possessed high thermal stability. The chromophoric pendants had endowed the polymers with novel optical properties. Upon photo excitation, the polymers emitted intense UV and blue light with quantum yield up to 0.98. Multilayer EL devices with a configuration of ITO/Polymer:PVK/BCP/Alq 3/LiF/Al were constructed, which emitted blue light ∼460 nm in high brightness and external quantum efficiency. Optimization of the device configuration further enhanced the performance and the maximum brightness and external quantum efficiency could reach 1065 cd/m2 and 0.85%, which are the best results for polyacetylenes attainable so far. By tuning the backbone rigidity and pendant interaction through molecular engineering endeavor, light emitting and liquid crystalline disubstituted polyacetylenes were successfully prepared, whose properties had been found to vary dramatically with the backbone structure and the mesogenic pendants. Incorporation of chiral appendages to the poly(phenylpropiolate) structure had generated optically active disubstituted polyacetylenes with strong helical chirality ([&thetas;] up to 11 × 104 deg cm2 dmol−1), which is extraordinary and rarely reported in the literature. |
