Department of Chemistry, Division of Advanced Materials Science, Pohang Accelerator Laboratory, Polymer Research Institute, and BK School of Molecular Science , Pohang University of Science and Technology , Pohang 37673 , Republic of Korea.
School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics , Georgia Institute of Technology , Atlanta , Georgia 30332-0400 , United States.
ACS Appl Mater Interfaces. 2018 Apr 18;10(15):12921-12929. doi: 10.1021/acsami.8b01196. Epub 2018 Apr 5.
Three triple bond-conjugated naphthalene diimide (NDI) copolymers, poly{[ N, N'-bis(2-R)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]- alt-[(2,5-bis(2-R)-1,4-phenylene)bis(ethyn-2,1-diyl)]} (PNDIR-R), were synthesized via Sonogashira coupling polymerization with varying alkyl side chains at the nitrogen atoms of the imide ring and 2,5-positions of the 1,4-diethynylbenzene moiety. Considering their identical polymer backbone structures, the side chains were found to have a strong influence on the surface morphology/nanostructure, thus playing a critical role in charge-transporting properties of the three NDI-based copolymers. Among the polymers, the one with an octyldodecyl (OD) chain at the nitrogen atoms of imide ring and a hexadecyloxy (HO) chain at the 2,5-positions of 1,4-diethynylbenzene, P(NDIOD-HO), exhibited the highest electron mobility of 0.016 cm V s, as compared to NDI-based copolymers with an ethylhexyl chain at the 2,5-positions of 1,4-diethynylbenzene. The enhanced charge mobility in the P(NDIOD-HO) layers is attributed to the well-aligned nano-fiber-like surface morphology and highly ordered packing structure with a dominant edge-on orientation, thus enabling efficient in-plane charge transport. Our results on the molecular structure-charge transport property relationship in these materials may provide an insight into novel design of n-type conjugated polymers for applications in the organic electronics of the future.
三种三重键共轭的萘二酰亚胺（NDI）共聚物，聚{[N，N'-双（2-R）-萘-1,4,5,8-双（二羧酸酰亚胺）-2,6-二基]-交替-[(2,5-双（2-R）-1,4-亚苯基）双（乙炔-2,1-二基）]}（PNDIR-R），通过 Sonogashira 偶联聚合合成，其中氮原子上的酰亚胺环和 1,4-二乙炔基苯部分的 2,5-位具有不同的烷基侧链。考虑到它们相同的聚合物主链结构，侧链对表面形态/纳米结构有很强的影响，因此在三种基于 NDI 的共聚物的电荷输运性质中起着关键作用。在这些聚合物中，氮原子上的酰亚胺环带有辛基十二烷基（OD）链，1,4-二乙炔基苯的 2,5-位带有十六烷氧基（HO）链的 P（NDIOD-HO）表现出最高的电子迁移率为 0.016 cm V s，与在 1,4-二乙炔基苯的 2,5-位带有乙基己基链的基于 NDI 的共聚物相比。在 P（NDIOD-HO）层中增强的电荷迁移率归因于纳米纤维状的表面形态的良好取向和高度有序的堆积结构，具有主导的边缘取向，从而能够实现有效的面内电荷传输。我们在这些材料中的分子结构-电荷输运性质关系方面的研究结果可能为未来有机电子学中新型 n 型共轭聚合物的设计提供了新的思路。
