The Study Of Preparing Tunable Fluorescent Polymers By AIE Molecules With Malonitrile Groups

Aggregation-induced emissive（AIE）materials are widely used in the organic dyes,two-photon fluorescence imaging,rare earth materials and bacterial killing due to their excellent optical properties.,AIE polymers have greater potential for development than other AIE materials because their characteristics of aggregation induced emission as both and the characteristics of polymers which was easier film formation,easier processing and richer functionality.At present,the intelligent materials is a popular project in material science.Intelligent materials,which was the functional materials that could respond to envirommental stimuli.Intelligent materials are generally divided into metal-based intelligent materials,non-metallic-based intelligent materials,and polymer-based intelligent materials.In the polymer-based intelligent materials,polymeric hydrogels have a three-dimensional cross-linking network structure of polymers and a multi-component system which was composed by media.All this characteristics has greatly expanded the application of intelligent materials.The fluorescent polymeric hydrogels（FPHS）are generally formed by embedding AIE small molecules into the polymeric hydrogels.As the signal unit of fluorescent,AIE small molecules can be used for quantitative detection of target analytes.At the same time,polymeric hydrogels provide a perfect carrier for AIE materials to play a role.Therefore,a sensing system which could respond perfectly to environmental stimuli could be constructed through AIE materials and polymeric hydrogels.The fluorescent polymeric hydrogels could respond to environmental stimuli,then resulting in volume changes,morphological changes and complex and tunable fluorescent changes.Therefore,fluorescent polymeric hydrogels have great potential in biosensing biological imaging,bionic robots,information encryption,information coding and other fields.The design of multi-color fluorescent polymeric hydrogels has also become a very meaningful work.The specific work is mainly divided into the following three parts:1.Through exploring the blue-shift fluorescent phenomenon of the TPAs-Vinyl-4CN copolymerized with NIPAm,and the TPAs-Vinyl-4CN is long-wavelength emitting molecule.Through comparative experiments and analogous experiments,the mechanism of the blue-shift of the malonitrile during the process of copolymerizing with NIPAm was discovered.During the polymerization process of TPAs-Vinyl-4CN and N-isopropylacrylamide,with the introduction of N-isopropylacrylamide,a double conjugate effect on the C=C-N functional group was generated with the fluorescent monomer.This made the C=C bond of the fluorescent unit very fragile,making it sensitive to some nucleophilic reagents,making TPAs-Vinyl-4CN or TPA-CN which was long wavelength emitting molecules with malonitrile functional groups more sensitive to water under the double conjugation effect.Due to the large amount of water carried by NIPAm,TPAs-Vinly-4CN,which produced double conjugation effect,undergoes a reverse reaction of the knovenagal under the attack of water,then changed TPAs-Vinly-2CHO into TPAs-Vinly-4CN.Finally,a fluorescent polymer with short wavelength emission is produced.The discovery of this mechanism is universal for most long-wavelength molecules containing malonitrile,and found the way for further exploring strategies to inhibit blue-shift fluorescence.2.After explored the mechanism of blue-shift fluorescence of long-wavelength emitting molecules containing malonitrile during the polymerization with amide chemicals in Part I,we found that introducing sodium acrylate（AAS）into the polymerization system can effectively inhibit the blue-shift phenomenon.This is because sodium acrylate（AAS）can be used as an absorbent to remove water from the system,protecting C=C from the nucleophilic reaction of water.On this basis,the synergistic relationship among fluorescent monomers and AAS and N-isopropylacrylamide was explored.In other words,keeping the amount of fluorescent monomer and AAS unchanged,increasing the amount of N-isopropylacrylamide in this system,the nucleophilic reaction of water molecules is artificially controlled,and a series of tunable fluorescent polymers are prepared,named poly₀to poly₂₅.The range of emission wavelength of this fluorescent polymers are 585 nm to 451 nm,so this polymers have tunable fluorescence in the solid state.When this fluorescent polymers are prepared into aqueous solutions,the range of emission wavelength is 575 nm to 435nm,so the aqueous solution of polymers also have tunable fluorescence.When the polymeric hydrogels gel₀～gel₂₅are prepared by aqueous solution of polymers with the introduction of PNIAm,the range of emission wavelength of the polymeric hydrogels are 551 nm～431 nm,so this hydrogels also have tunable fluorescence.The polymeric hydrogels has great potential in the fields of information encryption and information coding through their temperature sensitivity and fluorescence characteristics.3.The tunable fluorescent polymeric hydrogels gel₀～gel₂₅prepared in the previous part is prepared an information encryption material with the aqueous solution of tunable fluorescent polymer.As the aqueous solution of tunable fluorescenct polymers,they will changed their fluorescenct wavelength and fluorescenct quantum yield during the formation of hydrogels,this characteristic is particularly suitable for the presentation of encrypted information.The ultimately designed information encryption materials have excellent performance in both single-layer information encryption and complex 3D code.In addition,tunable fluorescent polymers also have good applications in the preparation of white-light emssion materials.