Organic Polymer Composite Fluorescence Fibers And Their Sensing Properties

Functional light-emitting polymer fibers have prosperous applications in the fields of light-emitting diodes,photovoltaic cells,transistors and chemo-/ bio-sensors due to their advantages of easy processing,controllable morphology and adjustable performance.Compared to the approaches based on wet-chemical solution-processed method,electrospinning technology has the advantages of simplicity,easy processing and large-scale preparation.One-dimensional electrospun polymer fibers with multifunction and high-performance can be applied to high efficiency organic laser,organic light-emitting diodes and sensors,so it has been attracted widely interests.Combining the efficient and stable blue light of organic conjugated molecules,it is of great value to construct conjugate molecular-based electrospun nanocomposite fibers,which has become an important research content to expand the application of organic photofunctional materials in the field of information sensing.In this thesis,a series of fiber devices were constructed by adjusting the multilevel structure and processing technology of different luminescent conjugated molecules.The intrinsic relationship between material processing technology and luminescent properties of composite fibers were studied and the internal relationship between the condensed structure of conjugate luminescent molecules and its fluorescence sensing were explored.The main contents are listed below.Firstly,inspired by the high luminescence efficiency of pyrene,a type of highly efficient blue light organic conjugate small molecule of Me Py Cz was designed and synthesized.Combining with the excellent electrospun ability of poly(ethylene oxide)(PEO)material,novel PEO/Me Py Cz polymer composite fibers have been prepared.These composite fibers own high luminescence efficiency and uniform porous morphology,and exhibit good selectivity on nitro compounds.As for p-nitrotoluene(p-NT)and nitromethane(NB),the fluorescence quenching efficiencies reach 91.98% and 85.45%,respectively.The fluorescence quenching of the composite polymer fibers should be attributed to the photoelectron transfer between the Me Py Cz fluorophore and the analytes.Moreover,its fast and highly sensitive response is related to the fast exciton migration,electron transfer driving force and microstructures in the Me Py Cz doped PEO fibers.The composite polymer fibers has good sensitivity and selectivity to nitro compounds,endowing the potential applications in the construction of portable explosive detectors.Secondly,based on the high efficiency luminescence of organic molecules in the first part,a series of high efficiency luminescence materials of polydiaryl fluorene were further designed.The effect of substituted alkyl chains with different length on the conformational transformation of the main chain of polydiaryl fluorine during electrospinning has been systematically studied.It is found that the 4-octyloxy-substituted poly [4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl](PODPF)has better planarization ability for the main chain.It is also found that the conformation of polyfluorene in PODPF/PVK composite fibers is related to the precursor solution in electrospinning,and the planar conformation of PODPF can be obtained by using 1,2-dichloroethane(DCE)as the precursor solution.Finally,the experiments of 2,4-dinitrotoluene(DNT)vapor fluorescence sensing shows that PODPF/PVK polymer fibers with planar conformation have higher fluorescence detection sensitivity,which proves that the multi-level ordered structure of organic conjugated polymer can effectively improve the fluorescence sensing efficiency.Thirdly,in the second part,it has been found that the electrospun composite fibers prepared using polyethylene carbazole(PVK)with rigid and thick ring side groups have large size,which make them difficult to realize an efficient chemical sensing.Therefore,PEO is chosen to be matrix because of its high flexibility,which could greatly improve the compatibility between PEO and poly diaryl fluorene.The rigid polydiaryl fluorene(PODPF\PHDPF\PNDPF)and the flexible PEO chain cross each other to achieve a highly physical cross network structure,which would inhibit the generation of phase separation structure in the electrospinning process.The prepared PEO/ polydiaryl fluorene composite fibers own uniform size and smooth surface morphology,and exhibit efficient and uniform blue light emission.PODPF in the fiber prepared by DCE shows a weak planarized conformational luminescence,but PODPF in the fiber prepared by DCE shows an amorphous phase state.This confirms that the molecular conformation of PODPF obviously depends on the solvent.In addition,these polymer fibers were employed to detect explosives.It was found that PODPF polymer fibers with ? phase had better detection sensitivity.At the same time,compared with the large-size PVK composite fiber,PEO/ polydiaryl fluorene polymer fibers had more excellent detection performance for DNT.Fourthly,a series of colorful luminescent composite conductive fibers PPFOH/ PVK are prepared using PVK as the matrix and poly(9-(4-(octyloxy)-phenyl)-2,7-fluoren-9-ol)(PPFOH)as a fluorescent reactive molecule.With the help of pi-pi supramolecular action,the composite fibers owning host and guest doping characteristics are successfully prepared by controlling the doping ratio of PPFOH to PVK,which can precisely regulate the aggregation characteristics between PPFOH molecular chains in the composite fibers.And it can achieve the regulation of host and guest luminescence from PPFOH in fibers.In these polymer fibers,the wavelength of high-energy luminescence of blue light with fluorene main chain is 400-460 nm,and the wavelength of luminescence of guest light with fluorene aggregator is 530-540 nm.It is also found that the conductivity of PPFOH/PVK composite fibers increases with the increment of PPFOH doping ratio.The PPFOH/PVK composite fibers can be fabricated into a fibrous yellow light-emitting device.In short,in this thesis,a series of polymer composite fluorescent fiber materials have been constructed,and based on tuning of the multi-scale structure of the fluorophores,the sensing performance of sensitivity and selectivity of the polymer fibers on explosion detection is systematically studied,and the intrinsic relationship between the detection sensitibity and interstructure are analyzed,and moreover,we explore the possibility in the fabrication of fibrous optoelectronic microdevice over the organic polymer composite microfibers.