含硫烷側鏈之３－烷基噻吩：單體與其聚合物合成與研究

Abstract

Poly-(3-alkylthiothiophene)s (P3ATTs) 為3號位置有一硫烷側鍊之噻吩共軛高分子。因其在硫烷基之硫原子相較於廣被研究的P3AT之烷基集團(CH2)有較小的凡德瓦半徑，P3ATTs將提共更好的主鍊共平面性以提高有效的共軛長度與分子間堆疊而進一步地提高載子遷移率。另外，硫烷基的π-拉電子特性將會降低其最高占據分子軌域（HOMO）和最低未占分子軌域（LUMO）能帶以提高其電化學穩定性與降低其能帶隙。 近期我們團隊研製出一新單體與對應之GRIM聚合反應以合成高立體規則性之poly(3-hexylthiothiophene) (P3HTT)。我們將此新方法學視為一擬活聚合法以提供較好的分子量控制。但其仍有許多問題尚未被解釋，包含其未被確定的聚合反應機制以及含有3-butylthiothiophene (3BTT)單體而導致的低純度P3HTT聚合物。在本篇論文中我們導入修正後的3HTT合成方法學以致出高純度之3HTT單體以利後續的高立體規則性P3HTT聚合反應機制探討。另外，我們也製備出高純度之3BTT與3-(2-ethylhexylthio)thiophene (32EHTT)以供其不同烷基測鍊對其相對應知P3ATT聚合物之物理性質探討。

Poly-(3-alkylthiothiophene)s (P3ATTs) are conjugated polymers possessing alkylthio side chain at 3-position of the polythiophene backbone. Because of the smaller VDW diameter of sulfur in the alkylthio side chain in comparison with the methylene group (CH2) of the alkyl side chain of the well-studied P3ATs, P3ATTs generally exhibit better backbone coplanarity, leading to elongated effective conjugation length and well-organized interchain packing to improve charge carrier mobility. Additionally, the π-electron withdrawing character of sulfur would lower both HOMO and LUMO levels to promote the electrochemical stability and to decrease the electronic band gap. Recently, our research group developed a new monomer and the corresponding GRIM polymerization procedure to synthesize highly regioregular poly(3-hexylthiothiophene) (P3HTT). The new methodology was expected to be pseudo-living so that good molecular weight control could be achieved. However, several issues are still wait to be solved, including the unclear and testified polymerization mechanism, as well as the existence of 3-butylthiothiophene (3BTT) monomer resulting in impure P3HTTs. In this work, we adopted a modified methodology to synthesize pure 3HTT monomers, enabling the studies in the polymerization mechanism and high purity and high regioregularity of P3HTTs. 3BTT and 3-(2-ethylhexylthio)thiophene (32EHTT) are also prepared in high purity to investigate the effect of side group on the physical properties of the resulting P3ATTs.