Preparation Of AIE Polymers With Electrofluorochromic Property And Application Research

Electrofluorochromic materials can be smart control fluorescence intensity or color changes with applying voltages.Because the electrical signal and fluorescence signal have high sensitivity,visualized,and regulating reversibility characteristics,electrofluorochromic materials have potential applications in advanced anti-counterfeiting,intelligent display and detection sensors.However,many electrofluorochromic materials suffer from fluorescence quenching problem in the aggregate state,which lead to the weak fluorescence signal in the process of color change and the low contrast of fluorescence switch,making them unfavorable for basic research and application development.Aggregation-induced emission(AIE)groups can be introduced into the molecular structures to obtain electrofluorochromic materials and devices with high fluorescence switching contrast,which has opened new vitality into the development of this field.This thesis mainly focuses on the preparation of a series of highperformance electrofluorochromic polymers by introducing AIE group,and the systematic study of their structure-performance relationship as well as exploration of the application of the materials in information storage and advanced anti-counterfeiting.The details contents are described as follows.First,two different AIE groups(tetraphenylethylene and dithiophenyldiphenylethylene)and triphenylamine derivatives were facilely introduced into polymers.With the increase of conjugated length,the polymer exhibits the red-shift of absorption and emission,and the voltage required for stimulus response is lower and faster response time.Thanks to its excellent response to electrical stimulation,the dual-mode information display device was fabricated by simple procedures.On the basis,we successfully fabricated a four-dimensional "color code" device with high capacity storage and multilevel anti-counterfeiting.Using the information multiplexing concept,the utilization space of the device was increased from two-dimensional physical space to four-dimensional space,so the high capacity storage was realized.Meanwhile,the device can realize multilevel transformation of various information contents under the variation of voltage,which improves the security of information.Second,through the design of the monomer,the thiophene monomers containing alkyl side chain or triphenylamine side chain were polymerized with tetraphenylethylene AIE group to obtaining with two thiophene polymers.The polymer with conjugated side chains exhibits redshifted absorption and luminescence,endowing them with low driving voltage and fast response time.The two polymers show high fluorescence contrast ratio due to the introduction of tetraphenylethylene group in the main chain.Based on the processability of polymer and its excellent response to electrical stimulation,a novel information security device was fabricated by solution spraying.Through the control of voltage,the dynamic change of information was realized successfully.The same initial information and subsequent information with different changes can be obtained by using the different spraying positions of the polymer in the two devices,which is beneficial to information advanced anti-counterfeiting application.Third,four carbazole-based polymers with different side chain ratios were successfully prepared.Due to the introduction of two different AIE groups in the main chain and side chain respectively,the polymers exhibit high luminescence intensity in aggregate state.Because of the different ratio of side chain,the polymers with different luminous color were obtained.In addition,the four polymers show the same fluorescence response voltages,and high fluorescence contrast and short response time,and maintained good stability within 50 cycles.Thanks to the excellent electrofluorochromic performance of the polymer,we successfully fabricated the information security and self-recovery devices.When applied voltage,the fluorescence quenching of polymer materials was observed,which is caused by electron loss and ion doping.After the voltage is removed,the polymer material layer is naturally restored to the original state during the ion extraction process.This work provides a new method for realizing the dynamic change and self-recovery of information application.Finally,through the design of monomers,we successfully prepared carbazole-based polymer system with double emission peaks.The luminescence color of the polymers can be adjusted and converted from ACQ to AEE characteristic.Furthermore,the electrofluorochromic device was constructed by the polymer materials.It was found that the different proportions of solvents in the gel electrolyte had a certain influence on the luminescent color of the electrofluorochromic device.Due to the carbazole cationic radicals are formed in the polymer layer with the process of electrooxidation,the intensity of the double emission peaks decreases,showing fluorescence quenching phenomenon.This work provides preliminary exploration of the effect of double emission peaks system under electrical stimulation and shows new design idea for the development of electrofluorochromic field.