Thermoreversible organogels from alkane gelators with one heteroatom

We have examined the abilities of five structurally simple molecules to for m thermoreversible gels with a variety of organic liquids. Each gelator is an acyclic alkane with one heteroatom. Of these, dioctadecylamine (2N) is t he most efficient gelator. At congruent to 3 wt % concentrations, it forms gels with alkanes, aromatic liquids, alkanols, methylene chloride, and sili cone oil that are stable in closed containers at room temperature for >7 mo nths. Each of the other molecules-octadecylamine (1N), trioctadecylamine (3 N), methyldioctadecylamine (MeN), and ditetradecylsulfide (2S)-is able to g el 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 hydr ogen-bond acceptor. Evidence for the importance of H-bonding interactions i n strands of the gels is found in infrared and differential scanning calori metric measurements on the gelators in their neat and gelled phases and fro m comparisons of gelation temperatures. Some of the gels were examined also by polarized optical microscopy. These molecules are structurally among th e simplest organogelators discovered to date. The fact that no more than on e point of potentially strong interaction can exist between molecules in th eir assemblies requires a severe modification of current models for the nec essary structural attributes of organogelators.