Ultrasound‐accelerated dehydrogenation of poly(1,3‐cyclohexadiene): efficient synthesis of poly(para‐phenylene)

AbstractThe effect of ultrasonication on the dehydrogenation of poly(1,3‐cyclohexadiene) (PCHD) with benzoquinones was examined with the aim of improving the rate of reaction at moderate temperature. The type of solvent and the ultrasound treatment strongly affected the dehydrogenation of PCHD. The rate of reaction of the dehydrogenation of PCHD with 2,3‐dichloro‐5, 6‐dicyano‐1,4‐benzoquinone (DDQ) or 3,4,5,6‐tetrachloro‐1,2‐(o)‐benzoquinone (TOQ) was markedly improved by the use of ultrasound, and poly(para‐phenylene) (PPP) and PPP–TOQ complex, respectively, were successfully obtained. The electron drift mobility for PPP was of the order of 10−4 cm2 V−1 s−1 with a negative slope, while that for PPP–TOQ complex was of the order of 10−3 to 10−4 cm2 V−1 s−1 with a negative slope. The dehydrogenation of PCHD with benzoquinones under ultrasonication is thus an effective method to obtain soluble PPP with a well‐defined polymer chain structure. Copyright © 2010 Society of Chemical Industry