| 研究課題/領域番号 |
26287097
|
|---|
| 研究機関 | 東京工業大学 |
|---|
研究代表者 |
VACHA Martin 東京工業大学, 物質理工学院, 教授 (50361746)
|
|---|
| 研究期間 (年度) |
2014-04-01 – 2018-03-31
|
| キーワード | conjugated polymers / photophysics / single-molecule studies |
|---|
| 研究実績の概要 |
Within the overall research goal of ‘Active control of optoelectronic properties of conjugated polymers via control of their conformation on single chain level’, research in the past year concentrated on conformational characterization of conjugated polymers and oligomers on individual chain level by single molecule spectroscopy. In the previous years of this project novel results were obtained using a derivative of polyfluorene, BDOH-PF. In the last year, the research concentrated on the prototypical polyfluorene derivative PFO with the aim to confirm the universality of the phenomena observed on BDOH-PF. It was found that the large variety of spectral forms observed on single chain level which reflects different types and extent of intrachain aggregation depend strongly on polarity and glass-transition temperature of the surrounding polymer matrix. For single chains of PFO in a solution it was demonstrated that changes from good to poor solvent cause almost complete transformation of the emission color from blue to green, and that the process is reversible, thus completely contradicting the conventional explanation of the green band emission as due to oxidation of the PFO main chain.
In addition, collaborations with various domestic research groups were initiated within the project, with the general aim to characterize the effect of conformation of a conjugated molecule or polymer on its photophysics. A promising new collaboration concerns photoresponsive conjugated molecule which changes its emission spectrum upon the effect of external mechanical stimuli.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The study of the single-chain conformation of conjugated polymers and its dynamics proceeded mainly according to the research plan. Single chains of PFO were studied dispersed in different polymer matrices representing good or poor solvents, in concentrated polymer solutions, or adsorbed on substrates and exposed to different solvents. These experiments were complemented with ensemble measurements of fluorescence lifetime and quantum yield, and with molecular dynamics calculations. In addition to the various types and extent of intrachain aggregates, intrachain charge-transfer state was proposed as one possible origin of the green emission of PFO.
The second aspect of the study, the simultaneous measurement and control of the conformation by atomic force microscopy (afm) proceeded by renovation of the afm setup, by optimizing the selection of cantilevers, covering the quartz surface with a thin layer of mica, and further efforts towards reducing vibrations.
The collaborative work on the novel photoresponsive conjugated molecule started on a system which spontaneously changes its emission color from blue to green between rigid and soft environments. However, the low quantum efficiency and limited stability prevented detection of the compound in the soft environment on single-molecule level.
|
| 今後の研究の推進方策 |
This year, the study of photophysical properties of conjugated polymers in relation to their conformation will continue. Effort will be concentrated on calculations with the aim to reproduce the spectral positions and spectral shapes of fluorescence in terms of excitonic coupling, exciton delocalization, inter-segment aggregation and charge-transfer character. Further, work will continue on efforts to characterize single chains or single nanoparticles of polyfluorene derivatives by simultaneous confocal and afm microscopy. The aim of the study will be mechanical manipulation of the conformation by the afm tip, and measurement of the resulting variations of the photophysical properties. The results are expected to provide an important feedback on the theoretical calculations of the various conformations of a polyfluorene chain and the corresponding emission spectra. A next stage involving single chain or single nanoparticle electroluminescence study using biased afm tip as an electrode will be also considered.
The collaborative work on the novel photoresponsive conjugated molecule will continue by exploring derivatives of the molecule that have their absorption and emission spectral regions shifted towards lower energies, with the expectation of increasing the compound photostability and quantum yield, and with the goal of achieving reliable single-molecule methods towards nanoscale probing of local rigidity and dynamics of polymers and soft matter.
|
| 次年度使用額が生じた理由 |
本研究に使用した消耗品が研究計画していたより安価で購入できたため、次年度使用額が生じた。
|
| 次年度使用額の使用計画 |
次年度使用額の主な使用計画として、原子間力顕微鏡での振動の問題をさらに解決するために防音対策のための消耗品を購入する予定である。
|
