己烷噻吩-己烷氧噻吩共聚物(P3HT-P3HOT)之合成機制探討與性質鑑定

Synthesis, Characterization and Mechanism Investigation of Poly(3-hexylthiophene-co-3-hexyloxythiophene) via Grignard Metathesis.

吳俊慶(Chun-Ching Wu)

指導教授 ： 戴子安

國立臺灣大學/工學院/化學工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01128

摘要

用格林鈉反應（Grignard Reaction）原理為基礎，然後以鎳（Ni）的錯合物當作觸媒合成出一系列同時具有烷基和烷氧基側鏈的噻吩共聚物(P3HT-P3HOT)，接著利用觸媒與分子量的關係實驗，發現共聚物由於受到了溶解度的影響，觸媒與分子量的相關性只限於某個分子量之內，而過了此分子量之值後，減少觸媒的量將再也不能提高共聚物的分子量。此外，我們也利用對於兩個單體不同的進料比例與實際比例實驗中，發現不管在任何不同比例下，烷氧基的噻吩的實際比例皆高於進料比例6~10%。後來再更進一步的實驗中，發現原來是因為烷氧基噻吩再形成格林納反應中間物時，具有比較好的化學選擇性，可以在反應時產生較多的可聚合中間物，而造成這個現象。最後我們利用了共聚合公式，將我們的實驗結果回推我們的反應係數，得到r1為1.2，r2為0.8，r1r2的乘積為0.96，得到此反應屬於一個高度隨機共聚合的行為(random copolymerization)，而不是交互共聚合(alternating copolymerization)或是塊狀共聚合(block copolymerization)。最後我們將不同比例的烷機和烷氧基側鏈的噻吩共聚物(P3HT-P3HOT)進行紫外-可見光光譜(UV-vis)、螢光光譜(PL)、熱裂解分析(TGA).循環伏安法(CV)、X光散射(XRD)和元件測試，元件效率等一系列的光電性質以及熱性質測試，發覺當烷氧基側鏈的噻吩在共聚物中比例增加時，光譜吸收會產生紅移的現象，再配合循環伏安法的測試，發覺加入烷氧基側鏈的噻吩會使其最高填滿軌域(HOMO)上升，整體能隙(band gap)下降，也了解到可以藉由控制烷氧基側鏈的噻吩在共聚物的內部比例來控制其最高填滿軌域以及能隙。此外我們發現由於烷氧基較易被氧化的關係，加入含烷氧基側鏈的噻吩會使熱穩定性變差，且經由X光散射的實驗發現加入烷氧基側鏈的噻吩會使整體的結晶性下降，最後，我們將此材料應用於太陽能電池中的活性層上面，發覺雖然降低能隙可以使原件吸收更多的光子，但由於最高填滿軌域的上升，造成元件的開路電壓(Voc)下降而影響元件的效率。

關鍵字

格林鈉反應 ； 烷基 ； 烷氧基 ； 噻吩共聚物 ； 隨機共聚合 ； 低能隙共聚物 ； 推電子性質高分子

並列摘要

Poly(3-hexylthiophene-co-3-hexyloxythiophene) (P3HT-P3HOT) was synthesized using Grignard reaction, and confirm the inert structure by H NMR. And we do a series of experiments about the relationship of catalyst and molecular weight to study the mechanism of copolymerization, due to the effect of solubility, we find that the copolymerization only obey the GRIM chain-growth phenomenon below certain molecular weight, after is number the molecular won’t grow up even you reduce the amount of catalyst. And we find the real ratio of 3-alkoxythiophene is always 6~10% higher than feed ratio in different molar fraction of comonomer experiment. And we assume the phenomenon is because of the 3-alkoxythiophene has well degree of regiocontrol than 3-alkylthiophene. That is, 3-alkoxythiophene will form more react Grignard intermediate than 3-alkylthiophene. And we also use copolymerization equation and our result to calculate the monomer reactivity ratios r1 and r2, and r1 is equal to 1.2 and r2 is equal to 0.8, the multiple of r1 and r2 is equal to 0.96, indirectly prove the copolymerization is a random copolymerization rather than alternating or block copolymerization. We choose five different fraction of copolymers and detect in UV-vis, photoluminescenece(PL), cyclic voltammetry(CV), thermal gravimetric analysis(TGA), X-ray diffraction(XRD) and solar device. And when we add alkoxythiophene into our copolymer, it will be red shift in optical absorption because of the electro-donation property of alkoxythiophene, and the highest occupied molecule orbital (HOMO) increase and the band gap decrease when we increase the mole fraction of alkoxythiophene, in other words, we can control the HOMO and the band gap by controlling the mole fraction of alkoxythiophene. In TGA test of thermal stability, because the alkoxy is more oxidize, the thermal stability become worse when we increase the mole fraction of alkoxythiophene, and also the crystallinity in the copolymers. Finally , we use the copolymers on the active layer of the organic solar cell, due to the reason of HOMO increasing, the Voc become smaller and lower the efficiency.

並列關鍵字

Poly(3-hexylthiophene-co-3-hexyloxythiophene) ； P3HT-P3HOT ； Grignard reaction ； random copolymer ； alkoxy-substituted thiophene ； low band gap copolymer

參考文獻

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