Preparation And Functional Application Research Of Fluorescent Elastomers Based On The FRET And AIE Effect

The research and application of fluorescent materials is an essential research direction to expand the functionalization of traditional organic elastomer materials,which has been widely used in photoelectric devices,bioimaging,anti-counterfeiting technology and reaction monitoring.The introduction of fluorescent molecules with different luminescence principles and properties into polymeric organic elastomer materials through rational molecular structure design is the key to realize excellent photo-stability,light controllable tunability,and is the main idea for functional applications.From the above background,in this study,two different types of fluorescent groups are introduced into conventional elastomeric materials by chemical covalent.Based on the different luminescence principles which exhibited excellent optical properties and functionality,the fluorescent elastomer materials have been used in multiple fields of technology,including anti-counterfeiting technology and reaction monitoring,which is of great practical value.The work is divided into two specific parts as follows:(1)Two polymers containing fluorescent groups,including polyurethane containing the anthracene(AN)side groups and polyimide containing the naphthalenediimide(NDI)structure were synthesized to realize multiple color changes with fluorescence through simply blending.Based on the FRET effect between AN and NDI groups,the coatings obtained tunable fluorescent luminescence phenomenon.AN possesses reversible photodimerization properties,the coatings exhibited multiple fluorescent response under photothermal stimulation.Based on the above principles,the optical properties of AN-TPU,the ratio of groups in AN@NDI-TPU,and the controlled modulation of the fluorescent color by the photo crosslinking were investigated to achieve the multiple fluorescence response.The results showed that the fluorescence resonance energy transfer effect of AN@NDI-TPU can be effectively established at the ratio of AN:NDI=2:1,demonstrating the red fluorescence,which emission wavelength is at 650 nm.Based on the properties of AN photo-crosslinking and thermal depolymerization,fluorescent coatings that can encode different information patterns and have an erasable-rewritable function under photothermal stimulation have been prepared,which is of great research value in the field of intelligent anticounterfeiting applications.Besides,the fluorescent coatings have excellent self-healing properties based on the FRET effect,hydrogen bonding and the synergistic movement of the chain segments,ensuring unavoidable damage during use.The self-healing process of the fluorescent coating was characterized by optical microscopy and laser confocal microscopy.The results showed that AN@NDI-TPU exhibited excellent self-healing ability under thermal stimulation at 50°C,while the cross-linked coating could still heal effectively at 100°C.The fluorescence visualization of scratch selfhealing processes has been realized.The preparation of fluorescent coatings with cross-linked structure and self-healing property based on the FRET effect greatly expands the functional applications of traditional polyurethane materials.The stimulus-responsive fluorescent coatings have great research value in the field of anti-counterfeiting technology.(2)The polymercaptopropylmethylsiloxane dimethylsiloxane with tetraphenylethylene as fluorescent molecules(TPE-PDMS-SH)as crosslinking agent are synthesized by rational molecular design.The crosslinking agent is suitable for the preparation of silicone elastomers based on thiol-ene click reaction by light curing.Based on the aggregation-induced emission(AIE)properties of the TPE-PDMS-SH,we introduced it into the light curing system as a fluorescent probe to monitor the reaction kinetics.Due to the competitive reactions between crosslinking and chain extension,the polymerization reaction kinetics of was characterized based on the principle which the different states of aggregation in the cross-linking reaction produces the strong fluorescence and the dispersed by chain extension exhibited the weak fluorescence.It has been investigated the effect of fluorescent molecule content,doping method and AIE properties on the light curing system.The results showed that TPE-PDMS-SH doped by chemical covalent with 0.3 wt%content was selected for the fluorescence monitoring system.During the exploration phase,small molecules were used as chain extenders to establish the fitted equations and analyze the kinetic parameters of the reaction.The results showed that the light curing process with 10% chain extender content fulfils the reaction mechanism of simultaneous crosslinking and chain extension reaction.The accuracy of the fluorescence monitoring results was verified through the crosslinking density.During the validation phase,a large molecular terminated thiol polymer was used as the chain extender.The different structures led to different reaction kinetic,which the most complete reaction was achieved with 0.1% chain extender content.The chain elongation kinetic was determined by gel permeation chromatography to verify the accuracy of the fluorescence monitoring results.A highly efficient and sensitive means of fluorescence monitoring of the kinetics of the crosslinking and chain extension reaction was validated and established through the different structural chain extender which caused different crosslinking and extension reaction.The different levels of aggregation also produced visual fluorescent luminescence during the light curing process.The fluorescent silicone elastomers have been prepared with the 140 k Pa～160 k Pa tensile strength and the 400%～450% elongation at break,providing mechanical properties for the tensile fluorescence response of the material.The fluorescent silicone elastomer exhibited excellent fluorescence response and reversibility at 400% tensile strain through multiple cycles of tensile response testing.The fluorescence monitoring system formulation can still be applied to the preparation of precision devices by 3D printing technology,widely extending the range of applications for fluorescent sensor devices.