藉由格林納置換鏈成長聚合法合成全共軛硬桿-硬桿雙嵌段共聚高分子PPP-P3BT及其自組裝行為探討與奈米混成系統之研究

Synthesis and Self-Assembly of All-conjugated PPP-P3BT Rod-Rod Block Copolymers via Grignard Metathesis Polymerization and Their Applications in Nanohybrid System

楊宜龍(Yi-Lung Yang)

指導教授 ： 戴子安

國立臺灣大學/工學院/高分子科學與工程學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.10304

摘要

硬桿-硬桿雙共軛嵌段共聚高分子是近幾年來發展起來的一種新型共軛聚合物材料，由於其特有的光電活性，以及通過自組裝實現可調控奈米尺度結構等特性，正逐漸成為人們研究的焦點。然而，與傳統的柔曲型嵌段共聚高分子相比，含有共軛鏈段之團聯共聚高分子由於本身具備的自組裝特性可進而有效藉由結構上的改變來調控其機械與光電特性，因而逐漸受到各界廣泛的注意。瞭解此類含有共軛鏈段之嵌段共聚高分子其自組裝特性以利後續的應用發展乃是相當重要的一環。然而目前在此研究課題上仍有許多未知的現象有待探索。本研究利用合成數種不同具備雙共軛鏈段之新穎嵌段共聚高分子來探討其自組裝行為，我們相信藉由本研究所得到的實驗結果，將有利於此類特殊高分子做更近一步之應用發展。
首先，在本論文中我們利用格林納聚合法合成一系列 PPP-P3BT硬桿-硬桿共軛嵌段共聚高分子，且經由NMR，GPC，以及DSC逕行鑑定。我們利用這一系列具有不同體積分率之PPP-P3BT雙共軛嵌段共聚高分子進行此一系統之自組裝行為探討。藉由小角度X光散射實驗發現其在空間中形成層板結構，並透過RuO4染色技術再由TEM電子顯微鏡下觀察此層板結構由PPP和P3BT兩相分離所形成。同時，我們也對所有樣品加熱進行小角度(SAXS)及廣角度(WXRD) X射線同步散射實驗，發現當PPP的π-π作用力消失後樣品中的層板結構也隨之崩解，但由於P3BT仍保有高強度之自身π-π作用力，因此可觀察到系統於有序-有序相轉換溫度時，原本層板結構轉換成奈米線結構。
接著，我們利用此系列雙共軛嵌段共聚高分子將高分子與碳六十衍生物PCBM在鄰二氯苯溶劑下製備薄膜，並分析其混摻形態。經由低掠角廣角(GIWAXS) X射線同步射散射實驗和TEM電子顯微鏡逕行分析，可得到相對於對照組P3BT，PPP-P3BT嵌段高分子更能有效分散PCBM。更進一步，利用高溫退火實驗，可於光學顯微鏡(OM)下，觀察單一聚合物P3BT/PCBM有巨觀相的聚集。此外，將PPP-P3BT應用於太陽能元件，將元件於攝氏180度下，退火6小時，仍無明顯元件效率衰退，具有極其優異之長期熱穩定性。亦於攝氏200度下，退火6小時，元件效率損耗僅有27.6%，因此在未來的應用上具有非常大的潛力。
最後，藉由上述所合成之PPP-P3BT雙共軛鏈段之新穎嵌段共聚高分子當結構模板，建構了一系列混成氧化鋅(ZnO)奈米粒子的有機/無機混成系統。初始，我們採用一種簡易的原位合成方法，探討ZnO/PPP-b-P3BT奈米混成系統之自組裝行為。以醋酸鋅(Zn(CH3COO)2．2H2O)為前驅物，而高分子P3BT嵌段部份之噻吩官能基能與鋅離子(Zn2+)進行螯合反應。接著，我們開發出利用低溫攝氏-20下退火三天，置備長序之PPP-P3BT/Zn2+奈米線，再藉由薄膜在大氣環境下加熱至220oC 三十分鐘以上，使鋅離子轉換為氧化鋅(ZnO)，成功利用加熱轉換的氧化鋅奈米粒子排列在高分子奈米線上。其中，我們利用TEM電子顯微鏡觀察高分子自組裝的行為，亦利用低掠角廣角(GIWAXS) X射線同步射散射實驗來研判氧化鋅奈米粒晶型(纖鋅礦)和PPP-P3BT嵌段共聚高分子之奈米線結構。如此，這些材料可應用於有機電子元件。

關鍵字

格林納反應 ； 硬桿-硬桿 ； 嵌段共聚高分子 ； 自組裝 ； PPP-P3BT ； PCBM ； ZnO ； 高分子太陽能電池 ； 長效穩定性

並列摘要

Recently, all-conjugated block copolymers of the rod-rod type has been developed into a new kind of conjugated polymer materials, and came into the focus of interest because of their unique and attractive combination of optoelectronic activity and controllable nanostructure formation. Compared with coil-based block copolymer systems, there is considerable interest for the co-self-assembly behavior of rod-rod block copolymer system in organic electronics applications. The co-self-assembly behavior of a rod-rod system is further complicated due to the presence of the anisotropic interaction between the rod blocks.
In Chapter 2 of this thesis, the self-assembly behavior of all-conjugated rod-rod poly(2,5-dihexyloxy-p-phenylene)-b-poly(3-butylthiophene) (PPP-P3BT) block copolymers was investigated. A series of monodisperse PPP-P3BT block copolymers synthesized via a sequential Grignard metathesis method (GRIM). Gel permeation chromatographer (GPC), nuclear magnetic resonance (NMR) spectra, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) was used to characterize the block copolymers. Small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) patterns as a function of temperature, the detailed phase diagram of the system was then established.
In Chapter 3 of this thesis, we demonstrated a new strategy for fabricating solar cell devices with well-defined double-channel like structure by using an all-conjugated PPP-P3BT block copolymer as an effective structure-directing template for geometrical manipulation of PCBM location. TEM, OM, and GIWAXS measurements were used to explore the detailed structure features and morphological changes of the PPP-P3BT/PCBM sample before and after annealing. Based on the accelerated aging experiments performed on the PPP-b-P3BT/PCBM system, extended thermal annealing was found to lead to slower formation of PCBM aggregations and longer device operational time. As a result, we believe that the use of this novel material provides a feasible way to enhance photovoltaic performance and shows potential for use in future optoeletronic applications.
In Chapter 4 of this thesis, we fabricated organic/inorganic hybrid that contains zinc oxide (ZnO) nanoparticles synthesized in the presence of a novel conducting-conducting diblock copolymer as a structure template for the hybrid system. A simple in-situ synthesis of the self-assembly behavior ZnO/PPP-P3BT nanohybrid systems were investigated. We use zinc acetate dehydrate (Zn(CH3COO)2．2H2O) as a precursor for ZnO nanoparticles and P3BT block as the functional host to chelate zinc ion. The chelated Zn2+ was converted into ZnO by heating in the air at 220 oC. Film samples of ZnO/polymer hybrid were prepared by the following method. First, we prepared a Zn2+/polymers solution, and then drop casted the Zn2+/polymers solution directly onto substrates. Then, the coated substrates were aged at -20oC for 3 days to form the Zn2+/polymers nanowires. Finally, the aged samples were then heated at 220oC for 30 minutes for characterization. The crystallinity and morphology of ZnO nanoparticles/polymer hybrid films were characterized by grazing incidence wide-angle x-ray scattering (GIWAXS) and transmission electron microscope (TEM). From the GIWAXS spectra, the polymer which dissolved in toluene has good orientation and Zn2+ was converted into ZnO (wurtzite crystal structure) by heating in the air. The TEM images also show that the self-aligned ZnO nanoparticles along the PPP-P3BT nanowires were successfully prepared. Thus, these materials may be widely applied in organic electronics.

並列關鍵字

grignard metathesis ； rod-rod ； block copolymer ； self-assembly ； PPP-P3BT ； PCBM ； ZnO ； polymer solar cell ； long-term stability

參考文獻

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