Synthesis And Application Of Diarylethene-Based Photoswitchable Multistate Fluorescent Polymeric Materials

Photoswitchable fluorescent materials are considered as a new class of materials that can be applied to data encryption,high-density optical storage,complex biological imaging systems,and anti-counterfeiting due to their excellent optical properties.To date,a variety of photoswitchable fluorescent polymers with different properties have been developed and reported.The structural units with different properties are modified into the polymers to meet different performance requirements.Currently,most of the photoswitchable fluorescent polymers display two-state(on-off or two-color)fluorescent switches.In these systems,their utilization in biological imaging were limited by the interference of background autofluorescence.In addition,photoswitchable fluorescent polymers with multiple emission states are popular in applications such as advanced optical memory and complex information encryption.Based on this,we constructed two different novel photoswitchable multistate fluorescent systems based on the principle of fluorescence resonance energy transfer,and systematically studied their photoswitchable performance,finally applied them to dynamic anti-counterfeiting,information encryption,data storage and other fields.The specific research contents are as follows:(1)Based on the FRET principle,by combining butyl acrylate(BA),styrene(St),4-(acryloyloxy)butyl 3-(3,3,4,4,5,5-hexafluoro-2-(2-methyl-1,1-dioxidobenzo-[b] thiophen-3-yl)cyclopent-1-en-1-yl)-2-methylbenzo [b] thiophene-6-carboxylate1,1-dioxide(SDTE),8-(3’,3’-dimethyl-6-nitrospiro [chromene-2,2’-indolin]-1’-yl)octyl methacrylate(SP8)as raw materials,one-step free radical copolymerization method was used to prepare a photoswitchable multi-state fluorescent polymer(PMFP).Due to the reasonable feed ratio of BA and St,PMFP has a relatively low glass transition temperature.The diarylethene units(SDTE)could be reversibly switched between non-fluorescent ring-opened form and green fluorescent ring-closed state(energy donor)under alternative 460 nm Vis.and 254 nm UV light irradiation.Meanwhile,the spiropyran units(SP8)could be reversibly changed between non-fluorescent ring-closed form and red fluorescent ring-opened state(energy acceptor)under alternative 525 nm Vis.and 365/254 nm UV light irradiation.Taking advantage of the effective fluorescence resonance energy transfer between donor and acceptor,it was assumed that PMFP could reversibly switch its fluorescence emission among three distinct states(no-emission,red,and green)under different light stimuli.Furthermore,we demonstrated a broad application of the photoswitchable multi-state fluorescent polymer in advanced data storage,multi-level information encryption,multi-color photorewritable patterns,and advanced anti-counterfeiting.(2)Three kinds of self-healing photoswitchable fluorescent polymers(P1,P2,P3)were prepared by one-step radical copolymerization method using butyl acrylate(BA),styrene(St),4-(acryloyloxy)butyl 3-(3,3,4,4,5,5-hexafluoro-2-(2-methyl-1,1-dioxidobenzo [b] thiophen-3-yl)cyclopent-1-en-1-yl)-2-methylbenzo[b] thiophene-6-carboxylate 1,1-dioxide(SDTE),4-(acryloyloxy)butyl4-(2-methyl-3-(2-(2-methylbenzo [b] thiophen-3-yl)-4-oxo-5,6-dihydro-4H-thieno[2,3-b] thiopyran-3-yl)benzo [b] thiophen-6-yl)-4-oxobutanoate(BTBA),and2-(((6-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)hexyl)carbamoyl)oxy)ethyl methacrylate(UPy).Due to the reasonable feed ratios of BA,St and UPy,the three types of photoswitchable fluorescent polymers have good mechanical properties and excellent dynamic bond self-healing ability.When SDTE units are irradiated alternately with 460 nm Vis.and 254 nm UV light,the emission was switched reversibly between the non-emission and green fluorescence state.When BTBA units are irradiated alternately with 525 nm Vis.and 365/ 254 nm UV light,the emission was switched reversibly between the non-emission and red fluorescence.In addition,the fluorescence behaviour of SDTE can be optically modulated by BTBA due to controlled fluorescence resonance energy transfer(FRET)from excited green fluorescent diarylethene(SDTE)to red fluorescent diarylethene(BTBA).Thus,the emission of polymer P1 can be selectively and reversibly switched between the non-fluorescent and green fluorescent states,the emission of polymer P2 switched between the non-fluorescent and red fluorescent states,and the emission of polymer P3 switched between the non-fluorescent,red and green fluorescent states after different alternating Visible and UV light irradiation.Compared with the PMFP in the first work,this multi-wavelength modulated polymer(P3)not only achieves reversible modulation of multi-level fluorescence in the polymer,but also has excellent thermal stability,outstanding long-term stability and fatigue resistance,and notable resistance to acid and base corrosion.Finally,we successfully applied these three types of photoswitchable fluorescent polymers in digital encryption,binary-trinary conversion encryption and QR-code encryption.