On the structure of oligophenylenes

We performed Raman spectroscopy on polycrystalline powders of bi-, para-ter -, para-quarter- and para-sexiphenyl under hydrostatic pressure up to 70 kb ar and from 10 K to 300 K. We show that the crystallographic phase transiti on temperatures can be determined with our experimental method. Furthermore , we report a structural transition with pressure that we attribute to a ch ange of the interring torsion potential from W- to U-shaped. The experiment al findings are confirmed by calculated Raman spectra and interring torsion potentials for the isolated oligomers as well as for the corresponding pol ymer in crystalline phase.