Preparation And Application Of Supramolecular Intelligent Hydrogels

Supramolecular hydrogel is a kind of soft material with three-dimensional network structure via non-covalent interactions,which endows the supramolecular hydrogel fantastic stimuli-responsiveness.The hydrogel shows potential applications in many areas,such as biological medicine,detector,software robot,actutor and so on.Thus,in this thesis,we focus on the design of hydrogelators and fabrication of stimuli responsive hydrogels.In addition,we prepared two-component hydrogels and explored their stimuli-responsiveness.This thesis shall contain the following three parts:1.Hydrogels self-assembled from an azobenzene building unit.We designed and synthesized two azobenzene derivatives(ADPMA and ADPSA)containing carboxyl structure as gelators.The molecules occur self-assembly via changing pH.ADPMA could self-assemble into hydrogel in acidic condition.We observed the micromorphology of ADPMA under different pH conditions via scanning electronic microscopy(SEM)and speculated the gelation mechanism and the arrangement of molecules by infrared spectroscopy(IR)and small-wide angel X-ray scattering(SWAXS).We also explored photo-responsivenesss of the system.Gels based on azobenzene always show gel-sol transformation upon UV irradiation,yet ADPMA shows different response.ADPMA shows typical photo-responsiveness based on photoisomerization of azobenzene in solution,however,ADPMA hydrogel shows stability.We characterized the systems before and after irradiation by UV light via SEM,UV-vis and SWAXS respectively.2.Photoresponsive hydrogels based on organic/inorganic supramolecular co-assembly.We conjugated cyanostilbene(CS)with decyltrimethylammonium bromide froming an amphiphilic molecule CSTEA and explored the coassembly of CSTEA with host molecules(CB[7]and ?-CD)and laponite whose surface is rich in anion charge.Transmission electronic microscopy(TEM)was used to observed the change of morphology.And UV-vis and fluorescence spectrum(PL)were used to characterize photophysical properties indicating that both host molecules and laponite increasing the fluorescent intensity of CSTEA.We also introduced high content of lapnite(3 wt%)into CSTEA,CSTEA/?-CD and CSTEA/CB[7]forming hydrogels respectively,which show excellent thixotropic property.Due to the photoisomerism of cyanostilbene upon UV light irradiation,the fluorescence of multicomponent hydrogels was rapidly quenched and recovered after annealing with heating.Based on this,we successfully prepared fluorescent printable hydrogel materials.3.Vapor-responsive hydrogels based on ?-cyclodextrin(P-CD).We investigated the gelation ability of ?-CD in different solvents.One-dimensional crystallization-induced self-assembly in N,N-dimethyl formamide(DMF)/water mixed solvent with specific proportion allows the formation of stable hydrogel.The hydrogel could selectively transform into crystalline precipitates upon exposing to aromatic solvent vapors.The phase transition is initiated through a cage-type to a channel-type single crystal transformation,in which the CH-?interaction between DMF and benzene ring confined within ?-CD dimers is regarded as the primary driving force.We demonstrated that this unique gel system could perform as an efficient senor and adsorbent for hazardous aromatic vapors indoors.Laponite coassembled with P-CD to generate binary organic-inorganic hydrogel composites,which kept the hydogel state yet showed haze evolution and strength variation toward aromatic vapor or heating-cooling treatments.