Synthesis Of Diselenide-crosslinked Smart Hydrogels And Its Property Investigation

Smart hydrogels are one of the typical stimuli-responsive materials,which underwent responsive behaviors with external stimuli,such as light,temperature,pH,humidity,force,redox etc.Their structure or state would change greatly,producing corresponding responsive signals such as changes of swelling rates,mechanical properties,colors,gel-sol and so on,which shows great application value in the fields of information technology,life sciences,and clinical medicine etc.In recent years,the research on Aggregation induced emission(AIE)materials has fundamentally overcome the problems of traditional Aggregation caused quenching(ACQ).AIE materials showed well application value in the fields of fluorescent probes,organic light-emitting diodes(OLEDs),ion recognition and so on.Tetraphenylethylene(TPE)is a typical AIE molecule,easy to be synthesized and functionalized,widely used to build various functional materials with AIE effect.Combining TPE with responsive hydrogels can be used to construct various stimulus-responsive fluorescent devices,which showed responsive fluorescence behavior under external stimuli.Diselenide exhibits multiple responsiveness to light,radiation,redox and other stimuli,which showed great application prospects in various fields,such as biomedical materials.self-healing materials,and photoelectric materials etc.Combining diselenide bond with hydrogels would provide final materials with multiple stimuli response,which shows great value in the field of smart materials.In this thesis,several stimulus-responsive hydrogels were designed and synthesized by combining the AIE effect with multiple responsive property of diselenide bonds.The specific research contents are as follows:(1)Synthesis and properties of AIEgen-functionalized diselenide cross-linked polymer gels as fluorescent probes.Firstly,the acrylate derivative of tetraphenylethylene.namely 4-(1.2.2-triphenylvinyl)phenyl acrylate(TPE-a).was synthesized.Secondly,the crosslinker(HEMA-Se)2 was prepared by the ring-opening reaction of y-selenobutyrolactone(y-SBL)by hydroxyethyl methacrylate HEMA.After that.the diselenide cross-linked poly(acrylic acid)gels containing TPE groups were successfully prepared by the copolymerization of acrylic acid(AA),TPE-a and(HEMA-Se)2.The obtained polymer gels were characterized by Fourier transform infrared spectroscopy(FT-IR)and scanning electron microscope(SEM).The redox responsive behaviors of polymer gels with different crosslink densities and TPE contents were studied.Through a comparative analysis,it was found that the lower crosslink density.the lower detection limit for redox agents,and the higher TPE content.the stronger fluorescence intensity was detected in the same concentration of redox agents.In addition,the polymer gels can be used as carrier materials with visual release effect for controlling release of drug.Vitro release experiments results showed that the fluorescence intensity in solution increased significantly as the release of loaded DOX,which indicated the visual drug release process.Finally,the biocompatibility of the polymer gels was investigated through cytotoxicity experiments.Compared with other selenium-containing polymers,the material prepared in this work showed lower cytotoxicity.(2)Synthesis and properties of mechanically responsive AIE polymer gels.Poly(acrylic acid)gels containing TPE groups were designed and prepared using polyethylene glycol diacrylate(Mw=1000)as the crosslinker for the aim of increasing the toughness.Rheological tests proved the successful preparation of the polymer gels.Due to aggregation induced emission effect of TPE molecule,the dry gels show strong fluorescence emission.The aggregation degree of TPE decreases after swollen,which resulted in the decreasing of fluorescence intensity.The fluorescence intensity decreases as swelling rate increases.Next.the dry gels were taken as the research objects to study the mechanical response behaviors of polymer gels.When a certain pressure was applied to the gel.the aggregation state of TPE groups changed.and the fluorescence intensity of the gel changed.It can be recovered after release the pressure.(3)Synthesis and properties of diselenide cross-linked gelatin composite hydrogels.Poly(aminoethyl acrylate)(PAEAA)chains were interspersed in the gelatin network by polymerization of aminoethyl acrylate(AEAA)in the gelatin solution.which formed semi-interpenetrating network hydrogels.Then,ring-opening of y-selenobutyrolactone by amino groups in side chain of hydrogel was achieved to form selenol groups.When exposed to the air,the selenol groups were oxidized to diselenide bonds.Gelatin composite hydrogel was obtained with physical and chemical double-crosslinking network.Several hydrogels were prepared by changing the crosslinking densities,types of crosslinker,gelatin contents,and monomer compositions.Their structures were analyzed by FT-IR while their mechanical properties were characterized by rheological tests.Due to the introduction of gelatin,the storage modulus(G')and loss modulus(G")of the composite hydrogel increased significantly,and the storage modulus(G')also gradually increased as increasing the gelatin content.Considering the bionic double-layer structure model,using the anisotropy of swelling between the two-layer structures,bionic double-layer smart hydrogels were prepared by the method of mold molding.The double-layer gels,under certain stimulating conditions,such as different pH environment,ultraviolet radiation,etc.,were bent in different directions and different degrees,which had significant application prospects in the field of bionic smart materials.