Construction And Research Of Photosensitive Gel System Based On Supramolecular Interaction

Photoresponsive supramolecular hydrogel is a material with a three-dimensional spatial network structure.Under external light stimulation,it can undergo controllable changes in properties,including optical properties,mechanical properties,and electrical properties.Photoresponsive supramolecular hydrogels are of great significance in many fields such as dye adsorption,drug delivery,ion recognition,logical light-controlled switching,and self-repair.Hydrogel materials with different functionalities and controllable transformations are the research focus of light-sensitive supramolecular hydrogels.Among them,the introduction of fluorescent properties into the hydrogel system is expected to be applied in the field of in vivo therapy.Therefore,it is very important to seek a green and safe strategy to prepare photoresponsive supramolecular hydrogels with fluorescent properties.In this work,we intend to use lignin as a fluorescent agent to prepare photoresponsive supramolecular hydrogels based on the host-guest supramolecular interaction between azobenzene(Azo)and cyclodextrin(CD).In this work,we intend to use lignin as a fluorescent agent to prepare light-sensitive supramolecular hydrogels based on the supramolecular interaction between azobenzene(Azo)and cyclodextrin(CD)host-guest.We used?-cyclodextrin(?-CD)modified enzymatically hydrolyzed lignin nanoparticles(?-CD@CEL-NPs),polyacrylic acid(PAA),and guanidino azobenzene(Azo-Gu)to construct Light-controlled switch and light-responsive fluorescent ternary supramolecular hybrid hydrogel.This work succeeded in preparing a light-sensitive supramolecular hydrogel with fluorescence characteristics through a green and safe method based on the phenomenon of biomass aggregation induced luminescence.It has potential application value in wound dressings,small molecule drugs and macromolecular drug carriers in vivo.The specific work of this paper is as follows:(1)Design and prepare the light-sensitive molecule Azo-Gu,study its photoisomerization properties and the host-guest interaction with?-CD.We first synthesize an azobenzene molecule with amino group(Azo-NH₂),and then guanidinate and ionize the amino group to obtain the positively charged Azo-Gu.The Azo-Gu photoisomerization process and the interaction process with?-CD were studied by ultraviolet-visible spectrophotometer(UV),1H nuclear magnetic resonance(¹H NMR),two-dimensional correlation nuclear magnetic and other characterization methods.(2)We prepared CEL-NPs with fluorescence characteristics through self-assembly of CEL,and grafted?-CD onto CEL-NPs to prepare?-CD@CEL-NPs.Study the morphology of CEL-NPs and the grafting of CEL-NPs by characterization methods such as scanning electron microscope(SEM),fluorescence spectrophotometer,X-ray photoelectron spectrometer(XPS),Fourier exchange infrared spectrometer(FT-IR),etc.Fluorescence performance before and after,and calculate the theoretical grafting number of?-CD by the method reported in the literature.(3)We successfully prepared PAA-Azo-Gu/?-CD@CEL-NPs photoresponsive supramolecular hydrogels with fluorescence characteristics,and studied the changes in optical and mechanical properties of the PAA-Azo-Gu/?-CD@CEL-NPs under the action of external light stimulation,to study the reciprocating gel-sol transition process.In this paper,the association constant between trans Azo-Gu and?-CD Ka>2000 M^-1,and the association constant between cis Azo-Gu and?-CD Ka<10 M^-1.CEL-NPs have a blue-green fluorescence of?460 nm(excitation wavelength of 365 nm),and the particle size range is below 200 nm and concentrated around 60 nm.?-CD was successfully grafted onto CEL-NPs,but the introduction of?-CD increased the overall number of electron withdrawing groups,resulting in a shift of the fluorescence range of?-CD@CEL-NPs by 30 nm from CEL-NPs.For green fluorescence.The number of?-CD grafted on the surface of CEL-NPs can be calculated by two calculations to obtain 5.31×103?-CD and 3.16×103?-CD.The area of CEL-NPs is 1.13×104 nm².PAA-Azo-Gu/?-CD@CEL-NPs supramolecular hydrogels can undergo a gel-sol reversible transformation under the reversible control of ultraviolet-blue light,and?-CD@CEL-NPs will emit under ultraviolet light irradiation Fluorescence,causing the gel to show bright yellow fluorescence.In addition,PAA-Azo-Gu/?-CD@CEL-NPs supramolecular hydrogels show good elastic deformation under a shear strain of 3.2%.Guaranteed to be under 3.2%shear strain(actual 1%shear strain),PAA-Azo-Gu/?-CD@CEL-NPs supramolecular hydrogel will increase its elastic modulus first and then decrease as the frequency increases.However,the gel-sol transition can still be controlled by ultraviolet-blue light illumination.