Study On Cyanostilbene-Based Photoresponsive Liquid Crystal Polymers Prepared By Ring-Opening Metathesis Polymerization

In recent years,ring-opening metathesis polymerization(ROMP)has developed rapidly due to its characteristics of living polymerization,and has been widely used in the synthesis of various structurally regular and functional polymers due to the advantages of mild reaction conditions and environmental friendliness.Fluorescent molecules containingα-cyanostilbene moieties,a class of linearπ-conjugated organic light-emitting emitters,have attracted extensive attention as unique fluorescent chromophores.On the basis of the vigorous development of small-molecule fluorescent liquid crystals,how to prepare a liquid crystal polymer with good mechanical properties and fluorescent properties has become an urgent problem to be solved.In this paper,two fluorescent liquid crystal polymer materials were constructed by ring-opening metathesis polymerization.The main research contents include:1.Preparation and study of photoresponsive fluorescent liquid crystal polymers A fluorescent liquid crystal copolymer PCHTP with side groups containing both mesogen andα-cyanostilbene group was synthesized by ring-opening metathesis polymerization method,and the triphenylamine group connected by the side chain cyanostilbene structure made the prepared PCHTP have obvious properties.Aggregation-induced emission(AIE)characteristics.At the same time,the linear structure of the flexible main chain and long spacer provides sufficient free volume for the system,and rapid reversible photoisomerization can be achieved under 450 nm and 365 nm light irradiation,accompanied by reversible changes in fluorescence intensity.In addition,PCHTP has the characteristics of high molecular weight and narrow dispersion(Mn=1.28×10~5,PDI=1.59).Therefore,fiber and film materials with good mechanical properties can be obtained by a simple solution or melting method without additional photo/chemical cross-linking,and further combined with the orientation control of liquid crystal molecules,the reversible regulation of linearly polarized fluorescence can be realized.2.Preparation and Properties of Multiple Responsive Fluorescent Liquid Crystal PolymersBased on the above research,a fluorescent liquid crystal copolymer PCHPD with multiple responsiveness was prepared by further changing the side group structure.Theα-cyanostilbene in the side chain of PCHPD contains a pyridine group,which makes PCHPD have obvious aggregation-induced fluorescence quenching.Characterized by acid-base reversible protonation(ACQ)and acid-base reversible protonation.The liquid crystal polymer solution exhibits obvious yellow fluorescence,and the fluorescence intensity of the solid decreases significantly.The fluorescence intensity of the liquid crystal polymer can be controlled by changing the ratio of the fluorescent monomer PD in the polymer.Combined with Gaussian simulation,the reasons for ACQ performance are discussed and analyzed.The fluorescence color of PCHPD changes after acid protonation treatment.Finally,the acid-base,light and solvent responsive characteristics of fluorescent liquid crystal polymers are used to demonstrate their applications in the field of information encryption.In summary,in this study,two high molecular weight fluorescent liquid crystal polymer materials were prepared by ring-opening metathesis polymerization.The molecular structure endowed them with good mechanical properties and fluorescence properties,and different application demonstrations were designed.The fluorescent liquid crystal polymers prepared in this study have potential applications in the fields of anti-counterfeiting and information encryption.