Study On Gelation Behavior Of Supramolecular Gels By Molecular Structural Units

As a soft substance,gel is favored by a wide range of researchers due to its wide range of applications in people’s essential life fields such as food and biomedicine.Supramolecular gels are the most important branch and are developing extremely rapidly.Supramolecular gels are three-dimensional network structures formed by the self-assembly of low molecular weight gel factors under the influence of various non-covalent interactions.Since their respective interactions are weakly reversible,it is easy to"interfere"with the gels,thus allowing their properties to be fine-tuned.In this study,two sets of novel small molecule gel factors were synthesized by designing modified gel factors and exploring the effect of the control of structure on the gel system.In this paper,gel factors with 12-hydroxystearic acid as the core,i.e.,compounds 1-5,were synthesized as potential low molecular mass gel factors.They were designed to have similar molecular structures with different alkyl chain lengths,in order to investigate the effect of the alkyl chain lengths in HSA-modified molecular structures on thermal stabilities and supramolecular structures of the organogels.Next,an amide-containing gel factor with aromatic unit as the core was synthesized,namely compound 6-8,designed to have the same rigid rings and different chain lengths,as well as different rigid rings and the same chain length potential low molecular weight gel factors.All compounds 1-5 could form stable organogels in several organic solvents.Especially,compounds 2 and 3 showed excellent gelation ability,and their minimum gelation concentrations in m-xylene solvent were 2 mg·m L^-1.The thermal stability and morphological studies showed that the alkyl chain lengths had an important influence on the supramolecular organogels.Moreover,Fourier transform-infrared technology and X-ray diffraction characterization were employed to study the main driving forces and molecular packing patterns of gelators in the gel phases.Compound 6 forms stable organogels in a variety of organic solvents,and due to its outstanding gelation ability,in particular,we investigated in detail the changes in its gelation behavior in methanol,ethanol and isopropanol solvents,and additionally explored the gelation ability of compound 6 in mixtures of solvents,which are less effective than single solvents.However,for compounds 7 and 8 the gelation ability was significantly less than that of compound 6.We found through thermal stability and morphological studies that the structural changes of rigid rings and chain lengths have an effect on supramolecular organogels.The main driving force of the gel factor in the gel phase was investigated by Fourier transform-infrared technique characterization.Through the above analysis and results,we are expected to study the important influence of molecular structure on gel properties and gel behavior in a more systematic way,and further understand the amide group in hydrogen bond as the main driving force.