FORMATION OF QUINOID FRAGMENTS IN VACUUM-DEPOSITED POLY-PARA-PHENYLENE FILMS - IR SPECTROSCOPY EVIDENCE

The structure of vacuum-deposited poly-para-phenylene (PPP) films prep ared from a high-molecular-weight PPP powder has been investigated by IR spectroscopy. It has been demonstrated that in IR spectra of PPP fi lms exhibiting intense luminescence an extremely strong band at 1375 c m(-1) is observed, which is not typical for currently known PPP modifi cations. Based on the IR, spectral data, the model of formation of a P PP chain with quinoid fragments in the ground electronic state is prop osed. The structure of defects that inevitably spring up during the be nzenoid-quinoid transition is discussed. High intensity of the band at 1375 cm(-1) is associated with the change in the order of the ''defec t'' C-C bond between adjacent quinoid and benzenoid units. (C) 1998 Jo hn Wiley & Sons, Inc.