新型含磷酸官能基之聚烷基噻吩/二氧化鈦混成材料之合成與性質研究

Synthesis and properties of novel phosphonic acid containing-poly(alkylthiophene)/TiO2 hybrid materials

周詩綺(Shih-Chi Chou)

指導教授 ： 邱文英

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00607

摘要

在眾多導電高分子中，聚噻吩因具有適切的光吸收特性及良好的電荷傳遞速率，因此廣泛地被應用為高分子太陽能電池的光敏性材料。然而，當它與無機半導體粒子掺合時，由於表面性質的迥異常造成巨觀上的相分離現象，進而嚴重影響兩材料間的光激電子轉移效率。本研究之主要目的即在於合成具有磷酸根之聚噻吩，然後與TiO2前驅物混和並進行溶凝膠反應，利用磷酸根與TiO2表面OH基之作用性以製備出新型聚噻吩- TiO2奈米複合材料。
首先，我們利用1,ω-dibromoalkane與3-bromothiophene反應合成出不同側鏈長之3-(ω-bromoalkyl)thiophene，再以NBS將其溴化為2,5-dibromo-3-(ω-bromoalkyl)thiophene，然後與P(OEt)3進行Michaelis-Arbuzov rearrangement反應，形成末端帶有磷酯官能基之噻吩單體，最後以McCullough法與2,5-dibromo-3-hexylthiophene單體進行共聚合反應，得到具有高規則度且帶有磷酯官能基之聚噻吩。本研究利用1H NMR、31P NMR圖譜，分析鑑定單體與高分子的分子結構，以GPC測定聚合物之分子量與分子量分佈，應用PL分析所合成之共聚合物與P3HT之放射波長圖譜。
進一步地，我們在高分子溶液中，利用non-hydrolytic溶膠凝膠法成長TiO2奈米粒子，合成一巨觀上均勻透明之有機-無機混成材料。我們由FT-IR以及 solid-state 31P NMR證明聚噻吩與TiO2之間的化學鍵結。UV-vis觀察到當TiO2與磷酸官能基聚噻吩產生鍵結時吸收波長並無明顯的位移現象。由PL圖譜觀察到側鏈長為6、8時，混成材料的PL圖譜並無顯著改變，而當側鏈長度增加為10個碳長時，發現有顯著位移與quench的現象；由SEM、TEM照片中觀察到TiO2可均勻分散在高分子網狀結構中，且粒徑分佈約為5至20 nm。而在TEM照片中，可觀察到TiO2在含磷酸官能基聚噻吩高分子側鏈長度為10個碳長時之分散性較好，證明磷酸官能基的存在可顯著地降低TiO2粒子之凝聚現象。

關鍵字

太陽能電池 ； 溶膠凝膠法 ； 聚烷基噻吩

並列摘要

Polythiophenes have been widely used as photo-sensitizer and electron donor materials in polymer solar cells, because of their excellent optoelectronic properties and high charge-carrier mobility. However, the inherent incompatibility of organic polymers and inorganic particles frequently causes severe phase separation upon physical mixing, thus leading to poor photo-induced charge transfer efficiency. In this study, a series of novel polythiophene-TiO2 hybrid materials were synthesized by the sol-gel reaction of titanium alkoxide precursor in the presence of phosphonic acid-containing poly(3-hexylthiophene) to increase the interactions between TiO2 particles and conjugated polymer chains.
2,5-Dibromo-3-(ω-bromoalkyl)thiophenes bearing different chain-lengths of alkyl side groups were synthesized by reacting 3-bromothiophene with 1,ω-dibromoalkane, followed by the bromination with NBS. Then, the terminal bromide group on thiophene monomer was converted to the phosphonate moiety by reacting with P(OEt)3 via the Michaelis-Arbuzov rearrangement. Finally, the phosphonate-containing regioregular polythiophenes were synthesized by the McCullough method using 2,5-dibromo-3-hexylthiophene and 2,5-dibromo-3-(ω- alkylphosphonate)thiophene as monomers. The chemical structures of monomers and polymers were characterized using 1H NMR and 31P NMR analyses. GPC was employed to investigate the molecular weight characteristics of polymers.
Polythiophene-TiO2 hybrid materials were prepared by the in-situ sol-gel reaction of titanium isopropoxide in the CHCl3 solution of polythiophene or phosphonate-bearing polythiophene. The bonding formation between phosphonic acid and TiO2 were confirmed by the FT-IR and solid state 31P NMR spectra of hybrids. Both SEM and TEM micrographs demonstrated that the presence of phosphonic-acid groups effectively prevents the macroscopic phase separation during the so-gel reaction, and showed that the size of TiO2 particles ranges from 5 to 20 nm. Moreover, the TEM pictures of hybrid materials revealed that TiO2 particles were better distributed inside the polythiophene matrix as the chain length of the alkyl side-arm increases to 10 carbons. Herein, a homogeneous and transparent hybrid material was successfully prepared, and the compatibility between TiO2 and polythiophene was greatly enhanced.

並列關鍵字

solar cell ； bulk heterojunction ； polythiophene ； phosphonic acid

參考文獻

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