发光聚合物与大笼型介孔硅构筑的纳米复合体系的光学性能研究

Incorporation of Light-emitting Polymer into Large Cage-Type Mesoporous Silica: Toward New Luminescent Nanocomposites

合成了具有规整六方棱柱形貌的大孔笼型介孔硅,通过液相自组装的方法将共轭聚合物链填入孔中,制备了无机介孔硅-共轭聚合物的纳米复合物.并利用SEM,TEM,XRD以及N2吸附等测试表征了介孔硅和复合物.通过研究这种介孔硅负载长链共轭聚合物的UV-vis光谱、PL光谱以及发光动力学,证明了聚合物链的聚集作用受到强烈的抑制而链活动能力减弱,链间激子的能量分布变窄;链间激子在介孔受限环境中寿命延长.激光扫描共聚焦显微镜研究发现复合物硅微粒的发光强度比聚合物聚集体的发光强度高20倍以上.纳米复合物在高温下仍然保持较高的发光强度,有效的减少了酮缺陷的产生.光稳定性测试表明该纳米复合物还具有较高的抗光氧化能力.

Light-emitting conjugated polymers confined in mesoporous environment create an opportunity for control of the polymer morphology for design of new functional composite materials with suitable qualities. A novel polyfluorene deriva- tive, poly[N-octylcarbazole-co-9,9＇-dioctylfluorene-co-l,3,4-oxadiazole] （PCFOz） was synthesized via Pd-catalyzed Sonogashira reaction in a mixture of 3,6-dibromo-9-octylcarbazole, 2,5-bis-（4-bromo-phenyl）-[1,3,4]-oxadiazole and 2,7-diethyne-9,9＇-dioctylfluorene with Pd（PPh3）2C12 and CuI as the catalyst. The large cage-like mesoporous silica FDU-12 with hexagonal prism morphology was successfully synthesized and modified with TMCS （trimethylchlorosilane）. The composite material was prepared by incorporating PCFOz into FDU-12 via one-step liquid-phase self-assembly method, and then fully characterized by mean of X-ray diffraction, nitrogen physisorption porosimetry, scanning electron microscopy （SEM）, transmission electron microscope （TEM） and thermogravimetric analysis. The absorption spectra of composites showed a red-shift and narrower band as compared to pristine film, indicating the polymer chains packing in a special style in the cage type pores with a narrower excitonic energy distribution. PL spectra of composite materials suggested that the cages could incorporate more than one chain but less interchain species formed in cages compared with aggregates in film. The fluorescence decay kinetics observed longer exciton lifetimes in the composites resulting from the reduced exciton mobility and strong torsional distortions. Fluorescence signal from composite materials observed by laser scanning confocal micro- scope showed 20-times-higher than that obtained from pristine polymer film. Temperature dependence of PL spectra of composites was examined by heating the samples from 40 to 450 K, resulting in less than 10% decrease of PL intensity but no spectra variation for nanocomposites, as compared with 52% decrease of PL intensity accompanying with green-band rising for pristine PCFOz. Photostability tests were performed under the radiation of highly focused UV beams, suggesting that the excitons in the PCFOz within the pores of FDU-12 possessed better environmental stability.