The highest transition temperature is observed for cyclo- hexane, i.e. a non H-bonding solvent: it is this interaction that sets the sol-to-gel transition, and, according to the frequency shifts reported in Table 2, it can be modulated by the steric hindrance and the rigidity of the R1 substitution (Scheme 1). This finding can represent an important control parameter when designing an organogelator that should work in a predetermined temperature range.
Altough thermal hysteresis is a very important property for practical applications of organogels, it has been rarely addressed by researchers in this field.
The favourable interactions of an apolar solvent, such as cyclohexane, with the apolar chains of the gelator 12 remain unchanged in the gel and in solution accounting for the lower hysteresis value as well as the lower DH of the transition (69.9 kJ/ mol for cyclohexane vs. 92.4 and 120.8 kJ/mol for diisopropyl ether/ethanol 9:1 and isopropanol, respectively). By increasing the polarity of the solvent, solvophobic interactions become more important together with the competition of the solvent for the formation of the hydrogen bond network.