Other aromatic polymers containing p-phenylene groups

OTHER AROMATIC POLYMERS CONTAINING p-PHENYLENE GROUPS 

Poly-p-phenylene is the simplest polymer containing p-phenylene groups. Several methods have been described for the synthesis of the polymer. One of the more successful routes is by dehydrogenation of poly-l,3-cyclohexadiene obtained by polymerization of 1,3-cyclohexadiene with a Zie er-Natta catalyst [1]  

A second method is the direct polymerization of benzene in the presence of combinations of Lewis acids with inorganic oxidizing agents [2]  

For example, benzene polymerizes in the presence of aluminium chloride-cupric chloride under remarkably mild conditions, i.e. 35-50 C. Polymerization is thought to be initiated by a proton (formed by reaction of traces of water and the Lewis acid) and to proceed through successive electrophilic substitution and oxidative dehydrogenation reactions  

Poly-p-phenylene is of interest because of its outstanding thermal stability. The thermal properties depend to some extent on the method of preparation, but generally there is little change on heating in air at 300-400°C. Since the material is highly insoluble and infusible (m.p. 530°C with decomposition), it is dilficult to fabricate and there has been little commercial development. 

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