Assembly And Disassembly Of Supramolecular Hydrogel Characterized By Fluorescence Spectroscopy

Nowadays, the control of self-assembly and disassembly of low molecular massgelators has been the subject of increasing attention in supramolecular hydrogels.Fluorescence spectroscopy is a novel strategy to monitor the process of assembly anddisassembly of supramolecular hydrogel system.In this paper, the self-assembly and disassembly of the supramolecular hydrogelswhich formed by N,N-dibenzoyl-L-cystine （DBC） was studied at first. Secondly, theselfassembly of DBC in micelles solution formed by traditional surfactant and Geminisurfactant N,N-didodecyl-N,N,N,N,N-pentamethy l-1,4,7-triazaheptane diiodide（S4）was investigated. Thirdly, the supramolecular hydrogels which formed by the complexionformation of Glutathione （GSH） and silver ions was studied. The results are as follows:1. The reversible transition of F-triggered disassembly and H⁺-triggered reassemblyof DBC can be easily characterized and monitored by using a Ru（Phen）₃Cl₂as afuorescent probe. The SEM images of DBC aggregates before F-triggered disassemblyand after H⁺-triggered reassembly show no signifcant difference. The results indicated thatthe transition of self-assembly and disassembly of DBC can be modulated by theconcentration of F and H⁺. Fluorescence spectroscopy is a novel strategy to monitor theprocess of assembly and disassembly of supramolecular hydrogel system.2.0.4wt%DBC can selfassemble in the micelles solution formed by traditionalsurfactant CTAB, TW80, SDS, the mixture of CTAB/SDBS, respectively. The intensity ofRu（Phen）₃Cl₂in DBC-CTAB/SDBS micelles hydrogel was double times larger than that inthe DBC gel without surfactants. The TGSof DBC gel with surfactant is lower than theDBC gel without surfactant, this can be ascribed to the fibers of DBC aggregates becomethinner and shorter arising from cross-tallogra-phic mismatch branching.3. Ru（Phen）₃Cl₂and8-amino-1-naphthalene acid sodium（ANS） have been used tocharacrize the coassembly structure formed by S4and DBC. The results showed that thefluorescence intensity of two probes has been enhanced by the coassembly structuresformed by the S4and DBC. The intensity of ANS exhibits a significant enhancement. Fluorescent optical microscopy （FOM） images showed that ANS distribute in the ball-likemicelles in the hydrogels, however, Ru（Phen）₃Cl₂was found in the fibers of aggregates.The results of disassembly of DBC aggregates indicated that S4can co-assembly withDBC.4. It was found that the gelation time of complex hydrogel GS-Ag（I） can be decreasedwhen using acetic acid buffer and PBS solution as gelation media. The results revealed thatthe fittest excitation wavelength red shift from350nm to370nm in GS-Ag（I）self-assembly process. It suggested that the shift of excitation wavelength could be used tomonitor the gelation process. The rheology spectra and FOM images confirmed theaccuracy of results of the excitation wavelength shift.