AN ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE STUDY ON POLYMERIZATION OF OLIGO-P-PHENYLENES

Polymerization of biphenyl, terphenyl and quaterphenyl has been studie d by the electrochemical quartz crystal microbalance technique and the influence of the concentration of starting material, temperature and polymerization potential on the polymerization reactions investigated. The results of a mechanistic analysis clearly show that the polymeriz ation at low potentials is dominated by a one-step dimerization reacti on, producing a film material consisting of short chains. When bipheny l is used as starting material, the yield of film layer is low due to the high solubility of the short phenylene oligomer intermediates. Wit h higher oligomers as starting material, the yield is higher, as the i ntermediates are less soluble. The yield of film material was lower wh en the concentration of biphenyl was increased or when a high polymeri zation potential was applied. By lowering the temperature during polym erization of biphenyl, the solubility of the oligomers was reduced and an efficient deposition process was observed. (C) 1997 Elsevier Scien ce Ltd.