Design And Preparation Of Stimuli-Responsive Polymeric Luminescent Materials And Their Application In Optical Anti-Counterfeiting

Polymer-based luminescent materials,owing to their superior plasticity,machinability,and resilience,are better suited for practical applications in comparison to their small molecule counterparts.Of the various types of polymer luminescent materials,a significant amount of academic interest has been garnered by stimuli-responsive polymer luminescent materials.Their unique attributes,such as self-responsive nature,adjustable response behavior,and diverse response modalities,have made them a prime focus for researchers.These materials have the capacity to modulate their optical properties in response to an array of external stimuli including light,electricity,heat,magnetism,and metal ions.Such adaptability paves the way for their extensive utilization in sectors like photoelectric information storage,optical devices,flexible electronics,and microelectronics.This study is dedicated to the design and creation of two distinct types of stimuli-responsive polymer luminescent materials.These materials,responding to light and metal ions respectively,exhibit dynamic regulation of luminescent characteristics.Their potential applications in repeatable,erasable fluorescence information,transparent flexible afterglow films,and screen printing are also explored in this research.The specifics of the research content include:1.Design,Synthesis,and Optical Anti-Counterfeiting Applications of Multi-Color Photo-Responsive Polymer Luminescent Materials Based on Hydrazone DerivativesIn this chapter,we have developed three novel hydrazone-based photoresponsive polymer luminescent materials denoted as P1,P2,and P3.Their respective monomers 1,2,and 3 incorporate carbazole as rotors and benzene,naphthalene,or nitrobenzene as stators.These were synthesized through free radical polymerization with acrylic acid in a ratio of 1:400.We have comprehensively studied the photoisomerization properties of P1,P2,and P3,both in solution and in thin film states.Our findings indicate that their structural Z/E isomerization is reversible under the influence of different light wavelengths,resulting in reversible changes in fluorescence intensity in the thin film state.Specifically,the fluorescence intensities of P1 and P2 films decreased to 1/3 and 2/5 upon irradation at 440 nm,respectively,and were restored to their initial fluorescence intensity after irradation at 340 nm.The fluorescence intensity of P3 film can be diminished to 3/5 upon irradiation at 490 nm and restored to the initial intensity by irradiation of 400 nm light.These reversible changes can be cycled up to 10 times without a significant loss of intensity.Given that P1,P2,and P3 possess distinct electron-absorbing groups,their fluorescence emission wavelengths are 482 nm（cyan）,494nm（green）,and 544 nm（yellow）,respectively.These materials demonstrate excellent film-forming properties.When dissolved in water and coated onto a quartz sheet,transparent and uniform films exhibiting varying luminous colors can be produced.By utilizing light irradiation of different wavelengths,information can be inscribed and erased on the film.Remarkably,the emission intensity of the written pattern does not significantly change even after 180 days,displaying exceptional stability.This unique attribute suggests promising potential applications of these materials in the realm of optical anti-counterfeiting.2.Metal Ion-Induced Dynamic Alteration of Optical Properties of Room Temperature Phosphorescent Polymer Materials and Their Potential Application in Optical Anti-CounterfeitingIn this chapter,we report the successful synthesis of a room temperature phosphorescence（RTP）polymer,P4,through free radical polymerization at a ratio of 1:100.The monomer is a compound derived from carbazole（an electron donor）linked with tripyridine（an electron acceptor）.The rigid environment and robust hydrogen bonding offered by polyacrylamide serve to restrict the vibration of luminescent molecules,stabilize the triplet excitons,and consequently facilitate RTP.In addition,we examined the photophysical properties of P4 after coordinating with various metal ions.The investigation revealed that P5,a coordination polymer created by the interaction of P4 and calcium acetate,exhibited a blue shift in phosphorescence emission from 493 nm to 473 nm,along with an increase in lifespan from 303.65 ms to 448.62 ms.In contrast,P6,a coordination polymer formed by P4 and zinc acetate,showed a phosphorescence emission red shift from 493 nm to 507 nm,with a lifespan reduction from 303.65 ms to 132.64 ms.We further compared the photophysical properties of the small molecular monomers corresponding to P4,P5,and P6 in both solution and thin film states,the phosphorescent emission spectra of the monomers at low temperatures（77 K）in dichloromethane solution(1.0×10^-5 M)are similar to those of their corresponding polymers,with complex 5 being blue shifted to ligand 4 and complex 6 red shifted to ligand 4.Overall,we have successfully implemented these materials in transparent flexible afterglow films and screen printing.These findings suggest that these newly developed materials could serve as potential resources for optical anti-counterfeiting applications in these domains.