Synthesis and characterization of poly(thienylacetylenes) with novel optical properties
Cha, John A.
Poon, Wan Hang
Wong, Henry N. C.
|Source||Preprints of Second East Asian Polymer Conference, Hong Kong, Hong Kong University of Science and Technology, Hong Kong, 12-16 Jan. 1999, p. 91-92|
|Summary||Polyacetylenes and polythiophenes are well-known conjugated polymers which display electrical conductivity, photoconductivity, electroluminescence, and optical nonlinearity. Certain substituted polythiophenes also exhibit thermo- and solvatochromism. Thus, the synthesis of conjugated poly(thienylacetylenes) which contain both acetylene and thiophene moieties is of particular interest because such polymers may exhibit unique and synergistic electrical, optical, and optoelectronic properties. In this study, we investigated the polymerization of two thienylacetylenes, namly, 3-(4-bromo)thienylacetylene (1a) and 3-(4-trimethylsilyl)thienylacetylene (1b) using Mo- and W-based catalysts (Chart 1). These monomers can be polymerized, depending on the reaction conditions, to polythienylacetylenes (2) and/or polyethynylthiophenes (3) which may be further polymerized to give polyacetylene-polythiophene ladder polymers (4). To avoid the formation of intractable mixtures of the above polymers, we succeeded in selectively polymerizing the acetylene triple bond in 1a and 1b while keeping the thiophene moiety intact to give 2a and 2b exclusively. These polythienylacetylenes exhibit novel light transmission characteristics in dilute solutions, with their cutoff wavelengths predictably tunable by simply changing their concentration.|
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