IR-SPECTROSCOPY STUDY TO PROVE QUINOID FRAGMENT FORMATION IN THIN POLY-PARA-PHENYLENE FILMS DEPOSITED IN VACUUM

IR spectroscopy is employed to study the structure of poly-para-phenyl ene (PPP) films deposited in vacuum on quartz and KBr supports. The fi lm structure is shown to significantly depend on the chemical composit ion of the original polymer and on the deposition conditions. Pretreat ment of the original PPP powder at 400 degrees C and vacuum deposition onto a support heated to 300 degrees makes it possible to prepare hig hly oriented PPP films containing quinoid fragments in the polymer cha ins. Formation of quinoid fragments entails changes in the IR spectra of PPP. An extremely intense band at 1375 cm(-1) is observed which in PPP with a chain length exceeding 20 is the most intense in the spectr um. A mechanism of quinoid fragment formation and a model of a polyphe nylene chain in which the quinoid state is the ground one are suggeste d.