Silole-containing poly(diphenylacetylene): Synthesis, characterization, and light emission

A disubstituted polyacetylene consisting of a poly(diphenylacetylene) backbone and a 1,2,3,4,5-pentaphenylsilole (SiC4Ph5) pendant, that is, -{(C6H5) C=C [C6H4O(CH2)(3)C equivalent to CSiC4Ph5]}(n)- (PS3DPA), was synthesized, and its light emission from both the backbone and the pendant was evaluated. The polymerization of C6H5C equivalent to CC6H4O(CH2)(3)C equivalent to CSiC4Ph5 with two ethynyl groups was effected with WCl6-Ph4Sn as the catalyst. The structure and properties of PS3DPA were characterized and evaluated by IR, UV, NMR, thermogravimetric analysis, differential scanning calorimetry, photoluminescence, and electroluminescence analyses. The ethynyl group of the diphenylacetylene moiety was polymerized exclusively, giving a soluble PS3DPA. The chloroform solution of PS3DPA showed a backbone emission that peaked at 522 nm, whereas the silole pendant was nonradiative at room temperature. The polymer did not show the aggregation-induced emission phenomenon, probably because the silole clusters were difficult to form when the polymer chains aggregated because of the very high rigidity of the main chain. Intramolecular rotations of the phenyl groups of the silole moieties were responsible for the nonradiative decay of the silole chromophore. The intramolecular rotations, however, could be largely restricted in a cooling process of the polymer solution, showing cooling-enhanced emission. The silole emission became dominant at lower temperatures. A multilayer electroluminescence device based on PS3DPA emitted a green light that peaked at 512 nm. (c) 2006 Wiley Periodicals, Inc.