Synthesis And Application Of Conjugated Polymers Containing Fluorene Building Block

Fluorescent conjugated polymers have distinct advantages in developing highly sensitive fluorescence chemosensors,and have been widely used as fluorescent sensing materials,because of their unique molecular wire effects combined with structural tunability and good processability.In this thesis,first,we designed and synthesized several new fluorescent conjugated polymers after review of the literature and the previous works of our groups.Then we selected the conjugated polymers and introduced them into the matrix polymers to prepare fluorescent fibrous membranes through electrospinning technique.Last,we explored the fluorescent properties of the conjugated polymers and investigated use of these unique conjugated polymers for rapid detection of aromatic amine in aqueous solution or in vapor.In the first part,we first synthesized the polyfluorene(PFO)by Suzuki coupling reaction.Then,we advanced a strategy of design and synthesis of three polyfluorene based conjugated polymers consisting of a fluorescent poly[fluorenyl-alt-p-phenyleneethynylene](PFPE)backbone as well as the long alkyl chains(i.e.PFPE-OR,PFPE-COOR,and PFPECOOH)through Sonogashira coupling reaction.PFPE-COOH with pendant carboxylic acid groups and long alky chains was selected for study of the fluorescence properties of polyfluorene based conjugated polymer.The results showed that aromatic amines such as pphenylenediamine(PPD)and aniline in aqueous solution quenched the fluorescence of PFPE-COOH significantly,whereas the aliphatic amines enhance the fluorescence of PFPECOOH.The fluorescence intensity of the polymer solution could be quenched to 90% or more by 0.1M PPD in aqueous solution within three minutes,and the detection limit reached 0.08925 mM.We designed and carried out a series of control experiments and Stern-Volumer analysis to study the behavior of fluorescence response,interference factors and sensing mechanism for this fluorescence sensory system.Finally,a model was proposed to explain the fluorescence sensing mechanism of different amine in aqueous solution.In the second part,we used three different fluorescent conjugated polymers with other polymer materials such as polylactic acid(PLA)and polyacrylonitrile(PAN)as matrix to prepare three fibrous membranes,denoted as PFO/PLA,PFPE-OR/PLA and PFPECOOH/PAN.By comparing the properties of the fibrous membrane and the screening of functional groups,we selected the PFPE-COOH /PAN fibrous membranes as the sensing material for further study.Next,we focused on detection of organic vapors using the PFPECOOH /PAN membrane.We found that PFPE-COOH/PAN fibrous membrane,which combined the excellent luminescent properties of fluorescent conjugated polymers and the large specific surface area of nano-material,had the excellent sensing performance in detection of ammonia and ethylene diamine vapors.For example,when the fibrous membrane was exposed to ammonia vapor with a saturated vapor pressure of 0.03699 kPa(21 °C)or higher,the fluorescence was clearly quenched in five minutes.The fluorescence of fibrous membrane was also significantly quenched in five minutes when exposed to a saturated vapor pressure of 2.104 kPa(25 °C)of ethylene diamine.