Abstract
Theoretical infrared (ir) spectra of trans- and cis- forms of poly(p-phenylene vinylene) (PPV) are presented, based on a single-period-chain model and harmonic potential with parameters transferred from p-divinyl benzen molecule. The out-of-plane degrees of freedom and the infrared intensities were included in the calculations. The calculations of polarized infrared spectra of cis- and trans-PPV do not show practically any difference. However, as the calculations evince the absence of the in-plane C-H bending infrared absorption band of trans-vinylene portion of experimental infrared spectrum of PPV, which is a consequence of a delocalized π-electron system (similarly to the case of trans-polyacetylene but not cis-polyacetylene), it seems that stereochemical structure of PPV is of the trans-form. Additional X-ray analysis is still necessary to support our conclusion.
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