Traditional organic chromophores and polymers with disc-like, coplanar geometry tend to be highly emissive in the dilute solutions but become weakly luminescent in the concentrated solution and solid states. On the contrast, conventional chromophores (such as silole) with non-coplanar structure exhibit strong fluorescence in the concentrated states due to the aggregation-induced emission (AIE) or AIE enhancement (AIEE) effect originated from the restricted intramolecular rotation (RIR) inherent from the chemical structures of the luminescent materials. To verify the influence of RIR on the AIEE properties, four approaches were attempted in this research.
First, copolymers PFN with alternative fluorene-naphthol unit was prepared through facile Suzuki coupling and was characterized to have AIEE properties due to the hydrogen-bond (H-bond) interactions among the inherent hydroxyl (OH) groups of the naphthol units. The H-bond interactions of PFN copolymer effectively restrict the molecular rotations and experimental variables (such as increasing solution concentration, introducing non-solvent water to solution, cooling and applying shearing forces during solvent evaporation stage etc.) effective in promoting the H-bond interactions result in the emission enhancement.
Second, the fluorescent PFN was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. By the effective H-bond interactions between the OH groups of PFN and the carbonyl functions of PVR. The molecular rotations of PFN can be effectively locked by large amounts of carbonyl groups in PVR. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt%) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN.
Third, novel vinyl polymer PTP with pendant AIE-effective tetraphenylthiophene (TP) group was prepared through radical polymerization. The resultant PTP polymer exhibits two discernible emission bands corresponding to monomer and aggregate emissions, respectively. The relative monomer to aggregate emission intensity of the PTP polymer in either the solution or the solid state depends strongly on the extent of aggregations. Increasing solution concentration results in the increasing extent of aggregation and the increasing aggregate/monomer emission ratio and also, the large emission enhancement due to the AIEE effect.
Finally, the TP-derived ammonium (TP-NH3+) cations are complexed with poly(sodium vinylsulfonate) (PSV) polyanion to generate ionic PSV-TP(x/y) systems with long-range electrostatic interactions between the cationic ammonium of TP-NH3+ and the polyanion of PSV. The fluorophoric TP units are associated with each other to form large aggregate domains stabilized by the long-range interactions. Introduction of water into dilute solution of PSV-TP in THF resulted in self-aggregated nanoparticles and the accompanied emission enhancement due to AIEE effect. Introduction of excess PSV polyanions promoted the self-aggregation of the TP fluorophores and resulted in the fluorescence enhancement. Nevertheless, addition of NaCl electrolytes causes the dissociations of the TP aggregates and the corresponding emission reduction. By controlling the additive, the blended PSV-TP film containing excess PSV has a high quantum yield of £XF = 0.83. In addition, the ionic PSV-TP complex film possesses high spectral stability without spectral variations after annealing at a high temperature of 270 oC.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0905111-125349 |
| Date | 05 September 2011 |
| Creators | Chien, Rong-hong |
| Contributors | Shiao-Wei Kuo, Anchi Yeh, Ker-Chang Hsieh, Lieh-Li Lin, Jin-Long Hong, Ming Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0905111-125349 |
| Rights | unrestricted, Copyright information available at source archive |
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