多壁碳纳米管-导电聚合物纳米复合材料中的相关构象和电荷输运
Correlated conformation and charge transport in multiwall carbon nanotube - conducting polymer nanocomposites
摘要：
用小角X射线散射（SAXS）研究了多壁碳纳米管（MWNTs）与导电高分子聚乙烯二氧噻吩-聚苯乙烯磺酸（PEDOT-PSS）复合材料的构象性质，解释了它们在低温下截然不同的电荷输运行为. SAXS研究表明细长的PEDOT-PSS小球在纳米管壁上组装，部分涂覆它们，从而限制了聚合物基质中纳米管之间的相互作用。这导致尽管存在金属多壁碳纳米管，但电荷传输主要由导电聚合物中的小极化子控制。在T > 4 K时，载流子在1D-VRH后的跳跃是明显的，这也引起了正磁阻（MR），由于MWNT的存在，具有增强的局域长度（~ 5 nm）。然而，在T < 4 K时，观察到非常规的正电阻率温度系数（TCR）归因于小极化子隧穿。在该温度范围内观察到的异常大的负MR被证实是由于准1D MWNT的存在，其可以帮助降低穿过纳米管-聚合物边界的隧穿势垒，从而导致大的离域。
英文摘要：
The strikingly different charge transport behaviors in nanocomposites of multiwall carbon nanotubes (MWNTs) and conducting polymer polyethylene dioxythiophene - polystyrene sulfonic acid (PEDOT-PSS) at low temperatures are explained by probing their conformational properties using small angle X-ray scattering (SAXS). The SAXS studies indicate assembly of elongated PEDOT-PSS globules on the walls of nanotubes, coating them partially thereby limiting the interaction between the nanotubes in the polymer matrix. This results in a charge transport governed mainly by small polarons in the conducting polymer despite the presence of metallic MWNTs. At T > 4 K, hopping of the charge carriers following 1D-VRH is evident which also gives rise to a positive magnetoresistance (MR) with an enhanced localization length (~ 5 nm) due to the presence of MWNTs. However, at T < 4 K, the observation of an unconventional positive temperature coefficient of resistivity (TCR) is attributed to small polaron tunnelling. The exceptionally large negative MR observed in this temperature regime is conjectured to be due to the presence of quasi-1D MWNTs that can aid in lowering the tunnelling barrier across the nanotube - polymer boundary resulting in large delocalization.
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