含硫烷側鏈之聚3-己基噻吩:精準性合成、微結構及光電性質之研究

Abstract

Poly(3-alkylthiothiophenes) (P3ATTs)為三號位置上含有硫烷側鏈的噻吩共聚物。屬於推電子基團的硫烷側鏈能提升噻吩共聚物主鏈上的電子密度，再加上硫與硫之間的非共價吸引力能促使更好的pi-pi堆疊，進而增加載子遷移率。因此P3ATTs被視為有能力取代傳統電子產品常使用的poly(3-alkylthiophenes) (P3ATs)。然而，儘管P3ATTs 和P3ATs的結構非常相似，P3ATTs卻不能以相同的製程方式合成出完美立體規則度的共聚物。 在本篇論文中將合成出一個嶄新的化合物2-bromo-5-iodo-3-hexylthiothiophene作為GRIM聚合的單體。有別於前人的合成方法，我們可以在較為平易近人的條件下獲得高立體規則度，設計的分子量以及狹窄的分子量分布。我們將系統化的研究溫度及反應時間在聚合時對於分子量以及分子量分布的影響。研究指出溫度會嚴重影響聚合活性，因此為分子量控制的關鍵。 藉由精準地控制分子量，我們聚合出一系列的P3HTT進而探討立體規則度和分子量對於光學吸收、電子能帶結構以及超分子組織狀況的影響。

Poly(3-alkylthiothiophenes) (P3ATTs), polythiophenes having alkylthio side chains at 3-position of a thiophene repeating unit, are expected to offer the corresponding electronic devices better performance than the mostly studied poly(3-alkylthiophenes) (P3ATs), as the sulfur atom of the alkylthio side chain could donate the electron density to the polythiophene backbone and the S(thienyl)-S(alkylthio) interaction would enhance stacking to improve charge carrier mobilities. Despite the similarity in chemical structures of P3ATTs and P3ATs, the methodologies commonly adopted for precise syntheses of P3ATs could not successfully produce well-defined regioregular P3ATTs. In this thesis, a new monomer 2-bromo-5-iodo-3-hexylthiothiophene, different from all the monomers used in the reported works in Rieke, modified McCullough and GRIM methods, is synthesized and which could be polymerized via GRIM methods with mild reaction conditions to produce poly(3-hexylthiothiophene) (P3HTT) with high regioregularity, designated molecular weight and narrow molecular weight distribution. By systematically investigating the influences of reaction parameters in GRIM polymerization on MW and MWD, including temperature and reaction time; it is found that the polymerization temperature is critical to the livingness of polymerization and which predominates the MW control. The success in precise synthesis of P3HTTs enable us to study the effects of regioregularity and molecular weights on the optical absorptions and electronic band structures as well as on the supramolecular organization.