探討以萘雙亞醯胺為基底之共軛高分子其合成、形貌與電子傳遞性質

Abstract

我們利用extended transition state−natural orbitals for chemical valence理論研究108個有機共軛分子晶體中的作用力，結果指出結構相似性主導了分子間作用力。我們據此為出發點設計了三個實驗性研究，以強化高分子晶粒（crystallites）間的聯結（interconnection）來增加共軛高分子的電荷傳導能力，進而改善有機場效電晶體（organic field-effect transistors, OFET）的工作性能。 第一個研究中，數種以naphthalene diimide為基底的高分子以側鏈刪節之策略合成出來。我們發現丁基側鏈的單元組成之提高造成π-order隨之遞減的同時，晶粒從專一的face-on轉變成碎小且各向異性，指出了π-interconnection之強化。從OFET的電子遷移率量測結果也可看出π-interconnection所造成的載子傳輸效率優化。 在第二個研究裡，我們合成共軛小分子N,N’-bisbutyl-2,6-bis([2,2’]bithiophenyl-5-yl)-1,4,5,8-naphthalene diimide (M)，並將其與P(NDI2OD-T2)混摻。兩者之結構相似性促使高分子與小分子之間存在一定程度的相容度，因此使得高分子與小分子間保存了電性耦合(electronic coupling)，達到有效地提供電荷傳導途徑的效果。 最後，我們嘗試在P(NDI2OD-T2)主鏈裡共聚pyrene單元。我們設想分子分餾機制與NDI–pyrene互補的作用力會互相競爭，進而影響高分子的薄膜微結構。此研究展示了利用共聚物中互補的作用力為一種新穎的方法來強化高分子的interconnection，向提升OFET載子傳輸性質的努力提供一條新的道路。 總體而言，這三個研究中的高分子形貌與微結構鑑定支持了interconnection增強的證據，建構出OFET的電子遷移率與薄膜形貌之間的關聯，進一步闡明了調控薄膜形貌以控制電荷傳輸性質的重要性。

The stacking principles are investigated theoretically with extended transition state−natural orbitals for chemical valence (ETS−NOCV) to examine the π- and lamellar stacking for 108 organic single crystals, suggesting that the resemblance in the molecular figure is responsible for intermolecular interactions. In light of this study, three independent works were performed with the aim of regulating the interconnection among conjugated polymers and further optimizing the organic field-effect transistor (OFET) performance. In the first work, fractional side-chain truncation is employed to furnish numerous naphthalene diimide-based polymers. As the increase of the butyl side chain in the polymer backbone, the π-order of the corresponding polymer thin film decreases gradually, while the π-interconnection is enhanced. The significant role of π-interconnection in the charge transport is emphasized. In addition, the π-anisotropy is transformed from face-on to isotropy, which can be rationalized by the geometric shape of polymer crystallite. The OFET results unravel the beneficial effect of π-interconnection to enhance the electron transport. In the second one, N,N’-bisbutyl-2,6-bis([2,2’]bithiophenyl-5-yl)-1,4,5,8-naphthalene diimide (M), was synthesized and blended with P(NDI2OD-T2). M is designed to resemble the monomeric unit of P(NDI2OD-T2) on the basis of the premise that structural similarity would promote their compatibility in the blends. This compatibility preserves electronic coupling through intermolecular interaction and establishes charge-transporting pathways as well. Lastly, pyrene moieties are incorporated into the P(NDI2OD-T2) backbone. It is envisaged that a competitive mechanism between molecular fractionation and the NDI–pyrene complementary interactions would occur and influence the microstructure of polymers. This work demonstrates a novel approach to intensifying the intrachain interconnection among polymers by the donor-acceptor (i.e., NDI–pyrene) complementary interactions, offering pathways for efficient charge transporting in OFETs. Overall, morphology characterization evidences that the interconnectivity in the conjugated system can be reinforced by the three approaches. The relationship between the OFET mobility and the morphological feature is constructed, elucidating the manipulation of thin-film morphology to control the charge-transport properties for conjugated polymers.