Effect of solvent isomers on the gelation properties of tri-aryl amine organogels and their hybrid thermoreversible gels with poly[vinyl chloride].

Abstract

The gelation properties of tri-aryl amine (TATA) in two isomers of dichlorobenzene, namely <i>ortho</i>-dichlorobenzene (<i>o</i>-DCB) and <i>meta</i>-dichlorobenzene (<i>m</i>-DCB), have been studied by calorimetry for mapping out the temperature-concentration phase diagram. It is shown that both systems behave differently, yet both form molecular compounds. The occurrence of these compounds is further demonstrated by neutron diffraction in <i>o</i>-DCB. Depending on the isomer used, X-ray investigations highlight a difference in the position of the diffraction peaks. The morphology observed by scanning electron microscopy reveals fibrillar systems in both cases, yet the fibrils' cross-sections are far larger in <i>m</i>-DCB with respect to <i>o</i>-DCB. The body of these results is discussed in light of current opinions on the role of the solvent. Ternary gels obtained with PVC have also been investigated by means of the same experimental approach. Calorimetry investigations and X-ray diffraction data show no significant difference for the behavior of the TATA moiety. The morphology studied by scanning electron microscopy allows one to distinguish clearly the TATA fibrils and the PVC network. This again confirms the possibility of preparing functional materials with an organogelator and a polymer through the making of hybrid gels.