The Gelation Behaviors And Self-assembly Mechanisms Study Of Some Low Molecular Weight Gelators

Novel supramolecular gelators like 2,4-(3,4-dichlorobenzylidene)-D-sorbitol(DCBS),1,3:2,4-Di(3,4-dichlorobenzylidene)-D-Sorbitol(DCDBS)and(R)-12-hydroxystearic acid hydrazide derivatives are designed and synthesized.The effects of salt,solvents and mechanical force on the gelation properties and self-assembly mechanisms of the gels formed with these gelators were reported and futher studied.The effects of salt on the gelatinization of DCBS was studied.DCBS showed pronounced hydrogelation.Addition of NaCl to the aqueous medium accelerated the gelation process and also caused the gel's morphology to change from globular to long fibers.In addition,the thermal properties of the hydrogels were improved with the addition of NaCl.A variety spectra showed that extensive aggregation of the phenyl rings with ?-? interactions was responsible for the gelation and hydrogen bonding was also a contributing factor in the gelation process.The presence of NaCl decreased the solubility of DCBS in water,thus enhanced the ?-? interactions,and finally increased the thermal properties of DCBS hydrogels.Wide-angle X-ray diffraction(WXRD)showed that the hydrogels had a layered structure which did not change with the addition of NaCl.Density functional theory(DFT)calculations indicated the possible molecular packing of the gelator in the nanofibers.The effects of solvents on the gelatinization of DCDBS was also studied.In polar solvents,smooth non-helical fibres morphologies with a rest CD signal was observed,whereas in nonpolar solvents,it were rope-liked left-helical fibres morphologies with a strong negative CD signal.The underlying mechanisms were further discussed by FTIR,fluorescence,X-ray diffraction(XRD),static contact angles and theoretical calculations.It was indicated that the conformations of DCDBS were different in different solvents.In nonpolar solvents,the whole molecule looks like a distorted T-shaped structure,whereas in polar solvents,the whole molecule shows a rigid plane-like structure.The different interactions between the gelator and the solvents could subtly change the stacking of the molecules and,hence,their self-assembled nanostructures.Based on these solvents effects,different polarity of solvents were mixed and twisted ribbons fibers morphologies with a medium strength CD signal was obtained,thus realized in situ tune nanostructures and control over the expression of chirality at supramolecular levelsFinally,the effects of mechanical force on the gelatinization of n-HSAH was also studied.The parent molecule(0-HSAH)is a much more efficient gelator than other derivatives and is a supergelator in ethylene glycol,where it forms self-standing gels with good self-healing,thixotropic,molding and load-bearing properties.The typical diffusion behaviors of small dyes in 0-HSAH/ethylene glycol gel blocks indicate a potential application of 0-HSAH in drug delivery field.While the other n-HSAH showed poor gelation abilities and failed to form thixotropic gels.POM,XRD and FT-IR studies reveal that 0-HSAH molecules may be arranged in a triclinic subcell with bilayer stacking.While the other n-HSAH(n = 2,6,10)molecules appear to be arranged in orthorhombic subcells with monolayers.These results show how simply structured gelator molecules can be tailored by subtle and seemingly small changes to produce a variety of gels with interesting properties that can lead potentially to valuable applications.