Observation of Molecular Complexes in Oligo-Phenylenevinylene (OPV) Organogels by Neutron Diffraction.

In an earlier report, we conjectured that oligo-phenylenevinylene (OPV) molecules bearing terminal OH groups may form molecular complexes in organogels prepared in benzyl alcohol. This assumption was based on circumstantial evidence only. In this paper, we report on new experimental evidence by means of neutron diffraction that unambiguously demonstrates this conjecture. After ascertaining that the thermodynamic properties of OPV gels are not altered by the use of a solvent isotope (hydrogenous vs. deuterated benzyl alcohol), we show that the neutron diffraction pattern in hydrogenous benzyl alcohol differs from that in deuterated benzyl alcohol. These patterns also exhibit additional peaks with respect to those obtained by X-ray. Comparison is further achieved with an OPV molecule without hydrogen bond terminal groups. In the latter case, no molecular complex is formed. These molecular structures may have a direct bearing on the differences observed in the gel morphologies.