Design,Synthesis And Properties Of Photosensitive Gelators

Supramolecular gels refer to the nanostructured aggregates that are self-assembled by low-molecular weight gelators in solvents,which are then wound together into a 3D network structure and effectively immobilize the solvents to gelate the whole system.As an important soft material,supramolecular gels can be modified by introducing different functional groups into the molecular structure of gelators to make different functionals materials.As a typical photoisomerization and photochromic molecule,azobenzene and its derivatives have unique advantages in constructing functional soft materials such as stimuli,photoelectric function and drug release,attracting more and more researchers'attention.In this paper,an azobenzene derivative with double-diketone structure and an azophenyl phenylalanine derivative were synthesized.In addition,the synthetic route was optimized,and the key compounds in the synthetic route were determined by NMR or MS.Due to the accumulation of the two compounds in the synthesis process,we only select azophenylphenylalanine derivatives to study their self-assembly behavior and properties.Through the self-assembly study of azophenyl phenylalanine derivatives,it was found that AZO-1 and AZO-2 were unable to form gels in a single solvent,among which AZO-1and AZO-2 had poor solubility in non-polar solvents,partially soluble in medium polar solvents,and completely soluble in large polar solvents.The compounds can form stable gels in the mixed solvent system of MeOH/H₂O?EtOH/H₂O?DMSO/H₂O?DMF/H₂O.Among them,the gelling ability of the mixed solvent system of MeOH/H₂O and EtOH/H₂O are better,followed by the mixed solvent system of DMSO/H₂O and DMF/H₂O.In different systems,the phase transition temperature of wet gel increases nonlinearly with the increase of water content in the system.Azophenyl phenylalanine derivative and its gel have good photoresponsive ability.Azophenyl phenylalanine derivative and its gel have good photoresponsive ability.Under the UV irradiation,the conversion rate of cis-trans isomerization of gels can reach up to 57%,and the gel structure of wet gels will collapse and the color will be deepened.SEM characterization showed that the microstructure of the formed gel was a large number of intertwined fibers with lengths ranging from tens of microns to hundreds of microns.Different molecular chirality shows different self-assembly aggregates,the assembly of AZO-1 has left-handed structure,and the assembly of AZO-2 has right-handed structure.It was found that when the ratio of Fe³⁺was greater than or equal to 1.0 eq,Fe³⁺would destroy the formation of gel.After standing for a period of time,the two will precipitate together,which provides a possibility for Fe³⁺adsorption removal.At the same time,the gel has a certain adsorption effect on rhodamine B and methylene blue dyes.