Synthesis And Property Modulation Of Fluorescent Functional Carbon Dioxide-Based Polycarbonate

Polypropylene carbonate（PPC）,which is formed via copolymerization of carbon dioxide（CO₂）and propylene oxide（PO）,is a promising environment-friendly material and is now industrially produced.However,the unsatisfactory thermal stability and mechanical properties of PPC have limited its applications.In addition,with the increased application of fluorescent materials in biology,chemistry,medicine and other fields,the demand for the functionalization of such materials has increased,which is a hot topic in the scientific community.Therefore,as described in this thesis,we use chemically modified terpolymerization to optimize the physical,thermal and chemical properties of PPC materials and study functional materials,especially fluorescent materials,in more depth;Further,modified PPC materials with fluorescent properties are synthesized by introducing fluorescent functional third monomer terpolymerization with CO₂and PO.Overall,this thesis focuses on the synthesis and performance study of fluorescent functionalized polycarbonate,and the following studies are performed:1.A dinuclear salen ligand backbone was prepared via a reaction between 3,5-di-tert-butylsalicylaldehyde and 3,3′-diaminobenzidine.A dinuclear salen[Co（III）TFA]₂ catalyst was successfully synthesized by combining trifluoroacetic acid（TFA）with Co,which functions as the central atom.This catalyst efficiently catalyzed the terpolymerization reaction between CO₂,PO,and a fluorescent functionalized third monomer.2.Fluorescein（F）was used as the third monomer for terpolymerization of CO₂ and PO via a one-pot method to synthesize a terpolymer with fluorescent properties（called PPCF）.The introduction of F could effectively improve the thermal and mechanical properties of PPC.The maximum weight loss decomposition temperature(T_d,max)increased by 25%,i.e.,from 270℃to333℃.In addition,the glass transition temperature（T_g）increased by 40%,i.e.,from 31℃to43.5℃.The elongation at break was reduced from 420%to 93%.Owing to its fluorescence properties,PPCF was used as a fluorescent probe to detect relevant metal ions in an HEPES solution（p H 7.2）,simulating the environment of living organisms.Our findings showed that PPCF exhibited a high selectivity for Fe³⁺ions.In addition,cytotoxicity and He La cell imaging experiments were conducted,and the PPCF polymer probe exhibited extremely low cytotoxicity and showed fluorescence inside the cells.This finding is important for studying polymeric PPC-like probes in biological applications.3.Conventional organic fluorescent materials are prone to aggregation burst phenomenon,which limits their applications.Thus,aggregation-induced light-emitting materials have been widely studied to avoid the aggregation-induced fluorescence burst effect of conventional organic light-emitting substances,cyanostilbene derivatives are the typical example of such compounds.In this paper,cyanostilbene-based monomer（2Z,2′Z）-3,3′-（1,4-phenyl）bis（2-（4-（oxirane-2-methoxy）phenyl）acrylonitrile）epoxy compounds（M）were first synthesized,and then PPCM fluorescent functional polymers were prepared using a one-pot method.The introduction of monomer M could improve the physical and chemical properties of PPC.In addition,studies on the fluorescence properties of PPCM showed that the PPCM fluorescent probe could be quenched by aniline and it exhibited anti-interference specific selectivity toward aniline.Thus,this probe can be used as an effective technique for detecting aniline.4.The fluorescent functionalized polymer PPCT was successfully synthesized by introducing a more rigid tetraphenylene monomer 1-（4-hydroxyphenyl）-1,2,2-tristyrene（T）into a dibasic copolymer system.Compared with the T_g values of polymers PPCF and PPCM,PPCT exhibited a 50%increase in T_g,indicating that it showed the best improvement in thermal and mechanical properties.In addition,PPCT showed good fluorescence quenching performance in the detection of Mn O₄^-,Cr O₄^2-,and Cr₂O₇^2-,especially for Mn O₄^-,with a low LOD(4.78×10^-8 M^-1).Thus,PPCT can be used as a probe detecting anions.