探討含有三噻吩的共軛側鏈其分子結構以及二維延伸共軛性質對於聚噻吩高分子之紫外/可見光吸收光譜的影響

本研究主要可分成兩個部分來進行：首先，我們利用全原子分子動力學(AAMD)模擬單一條高分子鏈在溶液無序狀態下之分子構形，並探討溶劑效應對於分子構形之影響；接著，再利用量子力學法來探討聚噻吩系列之共軛高分子其分子構形與紫外/可見光吸收光譜之關聯性。我們選擇以三噻吩為主軸的四個高分子材料PBTTTV-v、PBTTTV-h、H-PBTTTV-v與H-PBTTTV-h作為研究對象，藉此來探討平行或垂直主鏈之側鏈位向以及銜接處為乙烯基(Vinyl)或三個單鍵對於紫外/可見光吸收光譜的影響。藉由觀察全原子分子動力學所得到在溶液無序狀態下之高分子構形，可以得知PBTTTV-v、PBTTTV-h、H-PBTTTV-v與H-PBTTTV-h四個材料因受到銜接處上碳原子之立體阻礙的影響，使得其不論是在主鏈上的τMain chain_A與側鏈上的τSide chain_B皆擁有較廣的扭轉角度分布。比較特別的是，在銜接處的扭轉角度分析中，又以單鍵與單鍵之間的運動較為自由，其幾乎是呈現偏離共平面的90度(270度)附近，而引入乙烯基(Vinyl)能使其維持良好的共平面性(180度)。從這些結果中，能看到溶劑效應對於分子構形之影響。於紫外/可見光吸收光譜的結果中，觀察PBTTTV-v與PBTTTV-h之吸收光譜，可發現到其圖譜變的較為複雜，透過人工調控角度的測試，會得知其中存在著二維方向的延伸共軛，而於軌域分布中也看到電子雲分布會由主鏈延續到側鏈上。我們從中擷取片段以不同比例的方式進行組合，並與兩組不同聚合度之實驗結果相互比較，可以得知與實驗結果相符合。將銜接處改以三個單鍵後，可以發現到不同側鏈位向的H-PBTTTV-v(垂直)與H-PBTTTV-h(平行)皆有很相似的吸收光譜範圍，且其吸收光譜主要是受到主鏈與側鏈兩種片段結構所提供之貢獻所影響，而從其軌域分布中，也能得到良好的印證結果。在未來，我們將修正其中的扭轉角度，改從分子動力學達動態平衡後，擷取最大訊號峰值，再以量子力學法計算吸收光譜，從中探討並比較兩種不同之分子構形與紫外/可見光吸收光譜的變化。

關鍵字

二維延伸共軛性質；聚噻吩高分子；紫外/可見光吸收光譜

並列摘要

We employed all-atom molecular dynamics (AAMD) simulation and the quantum mechanical (QM) methods to explore the correlation between the molecular conformation and the UV absorption behaviors of terthiophene-based conjugated polymers. The four model systems examined here are PBTTTV-v, PBTTTV-h, H-PBTTTV-v and H-PBTTTV-h. We focus on the effects of side-chain architecture on the two-dimensional extended conjugation properties of the UV absorption spectra of polythiophenes. First, we observe the molecular conformation displaying disordered state of polymer chains within dilute solution via AAMD. In the PBTTTV-v, PBTTTV-h, H-PBTTTV-v and H-PBTTTV-h molecules, due to a large steric hindrance from the linkage between main chain and side chain, they have broader torsional angle distribution of main chain (τMain chain_A) and side chain (τSide chain_B). Because of the free motion of single bonds, the single bond linkages between main chain and side chain don’t intend to preserve a coplanar conformation as the H-PBTTTV-v and H-PBTTTV-h molecules. In contrast, as for the PBTTTV-v and PBTTTV-h polymers with vinyl linkage tend to keep a coplanar conformation. Then, we explore the UV absorption spectra of PBTTTV-v and PBTTTV-h molecules via QM. We notice that PBTTTV-v and PBTTTV-h have the two-dimensional extended conjugation properties in the UV absorption spectra, which make the UV absorption spectra more complicated. On the other hand, we observe the molecular orbital and discover the electron cloud may scatter along the main chain to side chain. As a result, we constitute several segments from the molecular orbitals by adjusting each segment’s fraction. The resultant UV absorption spectra of PBTTTV-v and PBTTTV-h show good match to the experimental results. When the single bonds are substituted for the vinyl linkages, the UV absorption spectra of H-PBTTTV-v and H-PBTTTV-h dimer show two peaks in the same range. The two absorption peaks are from either the main chain or the side chain. In the future, we will modify the torsional angle of molecular conformation within AAMD. We will systematically explore the correlation between molecular conformation and optoelectronic properties of PBTTTV-v, PBTTTV-h, H-PBTTTV-v and H-PBTTTV-h.

並列關鍵字

two-dimensional extended conjugation properties ； polythiophenes ； UV absorption spectra

參考文獻

[2] Li, G.; Shrotriya, V.; Huang, J.; Yao, Y.; Moriarty, T.; Emery, K.; Yang, Y. Nat.

J. Science 2007, 317, 222.

[4] Cheng, Y. J.; Yang, S. H.; Hsu, C. S. Chem. Rev. 2009, 109, 5868.

[5] Liu, H. W.; Chang, D. Y.; Chiu, W. Y.; Rwei, S. P.; Wang, L. J. Mater. Chem. 2012,

[7] Li, G.; Zhu, R.; Yang, Y. Nat. Photonics 2012, 6, 153.

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探討含有三噻吩的共軛側鏈其分子結構以及二維延伸共軛性質對於聚噻吩高分子之紫外/可見光吸收光譜的影響

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