Novel Two Component Reversible Heat-set Organogel Systems Based On SAD Derivatives And Alkyl Amine

Supramolecular gels are a fascinating class of intelligent soft materials, which are interconnected by multiple week non-covalent interactions, such as hydrogen bonding, metal coordination, van der Waals interactions, π-π stacking interactions, solvophobic forces（hydrophobic forces for hydrogels）. However, the dynamic and reversible nature of the non-covalent interactions that hold their network structures together results in the inherent ability of supramolecular gels to respond to external stimuli, such as temperature, pH, solvent, light, and redox reactions etc.A series of SAD were synthesized and the gelation tests were carried out by mixing SAD and R–NH₂ in 1:2 molar ratio in different organic solvents. The results clearly show that noly in aromatic solvents such as tetralin, benzene, nitrobenzene, and so on have the gelating abilities. Self-assembly behaviors and morphologies in gel state were studied in detail. In addition, a rational mechanism of the formation of heat-set organogels was proposed on base of our studies. We obtained some creative results, which were shown as follows:The obtained gelator salts revealed rarely observed reverse-thermal gelation（gelation with the rise of temperature） ability in various aromatic solvents, which are diffierent from the conventional gels（gelation with the decrease of temperature）. In non-aromatic solvents, SAD and R–NH₂ can not exhibit gelation behavior and thus can not form any gel. The quite different result reveals that solvent properties are important parameters in the process of the heat-set gelation. Additionally, it has been found that for a certain SAD-n, a primary alkyl amine with suitable length of tail chain is need to form heat-set gel in aromatic solvent. FT-IR, XRD, SEM, DSC etc. have been used to characterize these three types of gels. The results reveal that in this composite, there are three types of molecular interactions between SAD-6 and R14-NH₂, including electrostatic interactions, hydrogen bonds, and hydrophobic interactions. Moreover, the single-crystal diffraction data further indicates the result also.To tune the assembly structures and properties of this heat-set gel, we added different types of organic acids including fatty acids and dicarboxylic acids to this two-component system. It is interesting to find that when fatty acid such as dodecanoic acid, tetradeconic acid and so on is added to the two-component gelators, the reversible heat-set gel transforms to a reversible conventional gel. In addition, when fatty acid is replaced with dicarboxylic acid such as succinic acid, sebacic acid, SAD-6, SAD-10 and so on, the reversible heat-set gel transforms to an irreversible heat-set gel, which shows super-stability in the temperature range of 0–100 oC. The results of FT-IR, XRD etc. indicated that the addition of SAD-6 to gel system of 6·14 not only change the property of heat-set gel of 6·14, but also change the microstructure of this gel. Adding different types of organic acids including fatty acids and dicarboxylic acids to this two-component system, a unique gel system from which the formation of conventional gel and thermally super-stable gel can be achieved has been successfully built from the heat-set gels.