Luminescence Modulation Of Lanthanide Complex-doping Azobenzene-containing Polymers System

It is high promising to prepare optical modulation emission materials by incorporating lanthanide complex into photo-responsive azobenzene-containing polymers. In this thesis, the research work focuses on the investigations of the luminescence modulation of lanthanide complex-doping in different azobenzene-containing polymers system. The main contents included: luminescence modulation in lanthanide complex-doping azobenzene-containing homopolymer film system, lanthanide complex-doping azobenzene-containing block copolymer vesicles system, and lanthanide complex-doping azobenzene-containing polymer system with different absorption band. Detailed contents are described as follows:1. Lanthanide complex (Eu(DBM)3Phen) doping azobenzene-containing homopolymer film was fabricated by solution casting technology. After irradiation under linearly polarized light, the film was anisotropic. Then excited by non-polarized light, the typical emission of Eu(â…¢) of this film was polarized. It is resulted from polarized absorption by the ligands when the azobenzene polymer was oriented; the internal energy transfer from the ligands to the triplet state, and emission from the triplet state to the Eu(â…¢) ion is polarized.2. Azobenzene-containing amphiphilic diblock copolymer, poly(N-siopropylacrylamide)-b-poly{6-[4-(4-methylphenyl-zao)phenoxy]hexylacrylate}(PNIPAM-b-PAzoM), was synthesized by successive reversible addition-fragmentation transfer(RAFT) polymerization. In H2O/THF mixture, this amphiphilic polymer self-assembles into micro-vesicles. And the photo-induced luminescent vesicles can be obtained by incorporating Eu(DBM)3Phen in vesicles, where Eu(DBM)3Phen is located in the hydrophobic vesicular membrane which is composed of azobenzene polymer chain is located in the hydrophobic vesicular membrane which is composed of azobenzene polymer chain. The luminescence intensity of a single Eu(DBM)3Phen-doping vesicle can be modulated by irradiation of UV and visible light alternately, which was in-situ traced by fluorescence microscopy. Similarly, the luminescence intensity of the vesicles can be modulated. After analysis, this phenomenon is cause by the energy"redistribution"of the exciting light by both azobenzene for isomerization and lanthanide complex for emission. In addition, the luminescence from the self-assembled Eu(DBM)3Phen-doping vesicles exhibited a tendency to increase along with increased water content in the mixture solvent. Results show that the enhancement in luminescence intensity is attributed to the change in the hydrophobic environment within the membrane of the vesicles. With the increased water content, azobenzene groups were stacked more closely than before, the surrounding of Eu(DBM)3Phen became more hydrophobic, and the quenching effect of water was reduced.3. A strong push-pull azobenzene side chain monomer was synthesized. Its absorption peak was red-shifted compared with weak push-pull azobenzene compounds, which was also separated with the absorption peak of Eu(DBM)3Phen. Homopolymer and amphiphilic diblock copolymer containing this strong push-pull azobenzene were synthesized and Eu(DBM)3Phen-doping homopolymer films and Eu(DBM)3Phen-doping amphiphilic diblock copolymer vesicles were fabricated. The results show that Eu(DBM)3Phen-doping push-pull azobenzene polymer film can also emit polarized luminescence after photo-induced orientation. The polarization characteristics of the film can be modulated while the luminescence intensity was no change. For the Eu(DBM)3Phen-doping amphiphilic diblock copolymer vesicles, the luminescence of Eu(DBM)3Phen was not affected by the isomerization of the push-pull azobenzene moieties because the azobenzene did not absorb the energy of the exciting light.