Solvent effect on the morphology and function of novel gel-derived molecular materials

The gelation of two distinct hydrocarbon solvents by a new pi-functional molecule, followed by doping and measurement of conducting properties of the derived xerogel, reveals an important effect of the main gel component on the shape and organisation of the supramolecular fibres formed by the aromatic moieties. The gelator-a tetrathiafulvalene (TTF) derivative with two hydrophobic chains incorporating amide groups near the aromatic group-was also cast onto hydrophobic and hydrophilic surfaces from homogeneous solution and shows the dramatic influence of the concentration and surface on the aggregate formation, as revealed by atomic force microscopy (AFM). This observation underlines the advantage of using the gel route to prepare films of these materials. The doped xerogels show the effect of the solvent at the microscopic and macroscopic levels, as revealed by current sensing AFM and bulk four point conductivity measurements. The real polymorphism of the xerogels was confirmed by electron paramagnetic resonance (EPR) spectroscopy. In both materials, prepared from gels in (S)-limonene and n-hexane, and in contrast to a related compound with one hydrogen bonding group, the double hydrogen bond motif leads to materials which do not show structural phase transitions when heated. This feature shows the potential benefit of incorporating several hydrogen bonding groups on the phase stability of gel derived materials; to stabilise the metastable states to produce materials with different properties from a single compound by processing in different solvents.