Thermoreversible organogels from alkane gelators with one heteroatom

We have examined the abilities of five structurally simple molecules to form thermoreversible gels with a variety of organic liquids. Each gelator is an acyclic alkane with one heteroatom. Of these, dioctadecylamine (2N) is the most efficient gelator. At congruent to 3 wt % concentrations, it forms gels with alkanes, aromatic liquids, alkanols, methylene chloride, and silicone oil that are stable in closed containers at room temperature for >7 months. Each of the other molecules-octadecylamine (1N), trioctadecylamine (3N), methyldioctadecylamine (MeN), and ditetradecylsulfide (2S)-is able to gel at least silicone oil, and 3N and 2S also form stable gels with alkanols. The reason for the superiority of 2N as a gelator has been linked to its rodlike structure and ability to act as both a hydrogen-bond donor and hydrogen-bond acceptor. Evidence for the importance of H-bonding interactions in strands of the gels is found in infrared and differential scanning calorimetric measurements on the gelators in their neat and gelled phases and from comparisons of gelation temperatures. Some of the gels were examined also by polarized optical microscopy. These molecules are structurally among the simplest organogelators discovered to date. The fact that no more than one point of potentially strong interaction can exist between molecules in their assemblies requires a severe modification of current models for the necessary structural attributes of organogelators.