THERMAL-ISOMERIZATION OF CIS-POLY(PHENYLACETYLENE) - SCISSION OF POLYMER MAIN-CHAIN AND FORMATION OF 1,3,5-TRIPHENYLBENZENE AS A PYROLYSIS PRODUCT

After cis-poly(phenylacetylene)s (cis-PPAs) were heated at 180 degrees C for 1 h, the M(n)s decreased from 5000-53 000 to 2000-2600, 1,3,5-T PB corresponding to the cyclic trimer of phenylacetylene was formed, a nd the yields of the annealed PPA and 1,3,5-triphenylbenzene (1,3,5-TP B) did not significantly vary. A peak at 280 nm due to the phenyl ring and broad band up to 600 nn due to the pi-pi transition of the main- chain were observed in the u.v./vis. spectrum of cis-PPA. On the other hand, the absorption due to the conjugated main-chain disappeared for annealed PPA, though the phenyl group absorption was detected. The di sappearance of the main-chain absorption can be explained by deflectio n of the main-chain. Copyright (C) 1996 Elsevier Science Ltd.