The Polymerization of Toluene and Its Analogs Catalyzed by a Copper(I) Chloride–Aluminum Chloride–Oxygen System

The polymerization of aromatic compounds other than benzene (such as toluene, xylene, ethylbenzene, mesitylene, and biphenyl) was performed by using a copper(I) chloride–aluminum chloride–oxygen system which caused benzene to polymerize. Excess aluminum chloride, with respect to copper(I) chloride, was required for these compounds to polymerize, as was also true for benzene. For example, the treatment of toluene with aluminum chloride and copper(I) chloride (15:3:1 in molar ratio) under 1 atm of oxygen at 50°C for 24 h gave toluene polymer in 204% yield based on copper(I) chloride. This fact suggests that copper(I) chloride also worked as a catalyst in the case of the polymerization of toluene. The toluene polymer was obtained as both solid and liquid products, both of which were soluble in various organic solvents. The solid product has a complicated, crosslinked and “quinonoid-like” structure. On the other hand, the liquid product has a structure that is nearly identical with that of methylated poly(1,4-phenylene). Other alkylbenzenes gave the only liquid polymerization products, except for o-xylene which gave a small amount of solid products. The polymerization of biphenyl gave a low-molecular-weight poly(1,4-phenylene).