Pronounced Side Chain Effects in Triple Bond-Conjugated Polymers Containing Naphthalene Diimides for n-Channel Organic Field-Effect Transistors

다국어 초록 (Multilingual Abstract)

<P>Three triple bond-conjugated naphthalene diimide (NDI) copolymers, poly{[<I>N</I>,<I>N</I>′-bis(2-R<SUB>1</SUB>)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-<I>alt</I>-[(2,5-bis(2-R<SUB>2</SUB>)-1,4-phenylene)bis(ethyn-2,1-diyl)]} (PNDIR<SUB>1</SUB>-R<SUB>2</SUB>), 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<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, 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.</P>
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