Polyacetylene sensors

Polythiophene (PT) 20 can be regarded as a hybrid structure of cis-polyacetylene and sulfur, where the incorporation of the heteroatom leads to a much higher environmental stability of PT compared with that of PA [131], The outstanding physical and bulk properties make PT a desirable material for device applications like sensors, energy storage, solar cells, LEDs, NLO devices, and more [132], Due to the large number of possible technical applications, much effort has been made to tailor the properties of PT by synthesis. 

Conjugated polymers are powerfiil fluorescent materials, which makes them suitable for applications as chemical sensors. Chart 13.1 presents the structures of some typical polymers that are applicable for the detection of analytes at low concentrations. These polymers include poly(p-phenylene ethynylene), PPE poly(p-phenylene vinylene), PPV polyacetylene and polyfluorene. Those polymers bearing ionizable pendant groups are water-soluble polyelectrolytes. 

K-Conjugated polymers and oligomers are organic materials with many interesting and useful properties [1, 2], Examples of this class of materials include polyacetylene, polythiophene, polypyrrole, poly(phenylenevinylene) and their derivatives. Electronic conductivity, luminescence and nonlinear optical behavior are all observed in these materials and these properties have been exploited in applications such as electroluminescent devices (polymer light-emitting devices or PLEDs), electrostatic coatings, electrochromic windows, chemical sensors and memory devices [3-9]. 

A different method can be used for a doped polyacetylene semicon-ductive sensor [145], where PA is prepared by the polymerization of acetylene on the surface of a liquid catalyst [146]. The polymer film varies in its thickness from 0.1 to 5 mm, and after cleaning and drying it is doped to a nominal resistivity of 1 M 3.cm by bathing overnight in a solution of 50 mg I" in 100 ml hexane. The prepared film is punched into a small disc and housed in the body of a sensor in such a way that both contacts are placed on the one side and the sample on the other side of the polymer film. This mutual isolation of contacts and sample is only necessary in the case of liquid samples. 

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