導電高分子薄膜由於可撓曲、低成本、可大面積製造等優勢被廣泛研究於薄膜電晶體。自組裝單分子層能修飾基板表面能、降低基板表面缺陷、控制鍍膜品質、增進載子傳導效率外，最重要的功能為調控和有機半導體薄膜內的分子間作用力，進而決定分子排列。若不加以控制，導電高分子等軟性半導體分子巨觀排列的有序性不高，將產生許多形貌與電子結構缺陷，不利於載子之傳導。因此，透過系統性控制分子間作用力，增進半導體分子薄膜巨觀有序性與電子結構效能，是有機電子學領域非常重要的研究方向。
本研究使用導電高分子聚(3-己烷噻吩) 並自行設計合成單分子層，以系統性研究分子間作用力如何影響微觀成膜有序性。根據本實驗室林廷翰同學的研究，在相同的自組裝單分子層終端官能基下，不同單分子鏈長長度會影響聚(3-己烷噻吩)在基板上排列的異向性，其中以Methyl Adipoyl chloride (簡稱為O1S)鏈長因能與聚(3-己烷噻吩)側鏈有最佳互嵌作用，而呈現最佳有序性。然而，由本實驗室過往的研究發現，以相近長度的Octyltrichlorosilane (OTS)做自組裝單分子層時，聚(3-己烷噻吩)完全沒辦法沉積於基板。相較全為烷基鏈的OTS，O1S在近末端的位置有羰基C=O偶極矩。可推論自組裝單分子層極性官能基形成的偶極矩作用力為決定性差異，為了釐清分子間作用力例如何改變分子堆疊有序性，有必要系統性調變此偶極矩作用力，並觀察調變分子間作用力對成膜有序性的影響。
本研究要透過系統性設計不同自組裝單分子層，以呈現最佳有序性的O1S分子為準，固定各分子鏈長，再將C=O偶極矩以等間距遠離與高分子作用的表面，以此觀察弱化偶極矩對聚(3-己烷噻吩)排列造成的影響。
研究發現，隨著C=O偶極矩漸離末端，基板極性表面能項由39.67 (mN/m)降為30.15(mN/m)，且在不同製程溫度中發現，聚(3-己烷噻吩)有最高排列異向性的溫度區間也不同，而且此溫度區間可系統性對應偶極矩與表面的距離。因此，本研究成功連繫了控制分子間作用力與排列有序性的物理參數，為有機電子元件效能調控提供了重要的指標性意義。

Lack of ordering is the critical bottleneck of soft electronics. Morphologic imperfections of semiconducting polymers in manufacturing processes cause electronic defects and therefore, lead to low performance in electronic devices. To suppress these stacking faults among molecules, the control over intermolecular interactions between semiconducting polymers, their solvents, and substrates in microscopic regime are the key toward highly ordered thin films. Through systematically modulating microscopic forces between molecules, ordered polymeric films can be illustrated. Our study found that the terminal functional groups and chain lengths of self-assembled monolayer (SAM) on substrates will strongly affect the order of poly(3-hexanethiophene) (P3HT). Among three chosen SAM molecules with same terminal group but different in length, the chain length of methyl adipoyl chloride (referred as O1S) showed the best ordering. Compared to our previous studies, octyltrichlorosilane (OTS) with the similar chain length as O1S cannot properly align P3HT, indicating improper intermolecular forces in between. The key difference comes from the terminal carbonyl group on O1S and the inert alkyl on OTS. The decisive difference arises from the dipole moment of C=O double bond on carbonyl group.
In this study, we systematically elongate the separation of C=O group from the interactions on the interface between SAM and P3HT in solution. We chose and named the SAM molecules as O1S, O3S, and O5S. They have identical chain length but differ in the dipole spacing toward SAM/solution interface. Obviously, the weakened interactive dipole moment will modulate the local molecular arrangement of P3HT molecules as well as their ordering.
Our result showed that, O1S, O3S and O5S, were all able to arrange poly(3-hexanethiophene) (P3HT) in good order, but the best ordering condition of each appears in different temperature range, corresponding to the systematically weakened intermolecular interactions between C=O dipole and P3HT molecules. Our methodology reveals a reliable strategy toward the control over complex intermolecular interactions.

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