Key role of solvent type in organogelation

In this paper we again assess the role played by the solvent type in the organogelation process of photo/electroactive oligo (para-phenylene vinylene) (OPV) molecules. In this aim we have investigated gelation in benzyl alcohol, a polar solvent, and trans-decahydronaphthalene, an apolar solvent. Several techniques have been used: DSC, SEM, AFM, TEM, X-ray diffraction, UV-vis, and fluorometry. We have observed that the gel thermodynamics (T-C phase diagram), morphologies, molecular order, and optical properties differ considerably with the solvent type. The results are discussed by considering the interaction of the solvent with the different moieties of the OPV molecule. The reason why fibrils are obtained instead of 3-D crystals is also considered on the basis of micro-diffraction experiments performed by electron microscopy on finite aggregates.