Hydrogen trans-polyacetylene

In the following Section we present results of the application of the method to two model prototype systems, namely molecular hydrogen chains and all-trans polyacetylene. 

Fig. 4.1 The chemical structures of several relevant polymers are illustrated. There is a carbon atom at each vertex, and the hydrogen atoms are not shown. PE(CHf polyethylene, or PE, with only the C-H single bonds shown PA trans -polyacetylene PPV poly(p t -phenylenevinylene) and PPP poly(pita -phenylene). The lower three polymers are conjugated, according to the alternating single and double bond system.

The size of electroconductivity compressed samples MoClj j(C3(, jHgQ j), measured at a direct current at a room temperature-( 1.3 3.3) 10 Ohm -cm is in a range of values for a trans-polyacetylene and characterizes a composite as weak dielectric or the semiconductor. The positioned size of conductivity of samples at an alternating current tr = (3.1 4.7)-10 Ohm cm can answer presence of ionic (proton) conductivity that can be connected with presence of mobile atoms of hydrogen at structure of polymer. 

The polymer trans-polyacetylene, trans-(CH)j. contains a very long chain of alternating single and double carbon-carbon bonds. The term trans refers to the configurations of the two hydrogens bonded to each pair of doubly bonded carbons (Fig. 17.7). Analysis of the... 

Fig. 5 Chemical strucmres of some most common ECPs in their neutral state, hydrogen atoms are omitted for clarity, a Trans-polyacetylene, b PPy, c PEDOT and d PAn...

Thermogravimetric curves for the polyacetylene, there are two exothermic peaks at 145 and 325°C [16]. The first of these corresponds to an irreversible cis-trans isomerization. Migration of hydrogen occurs at 325°C, open chain and cross-linking without the formation of polyacetylene volatile products. The color of the polymer becomes brown. A large number of defects appears. In the infrared spectrum there are absorption bands characteristic of the CH, CH3, -C=C- and -C2H5- groups [16]. 

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