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Type: article × Publisher: Amsterdam [u.a.] : Elsevier × Subject: Electric conductivity ×

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    Liquid sensing: Smart polymer/CNT composites
    (Amsterdam [u.a.] : Elsevier, 2011) Villmow, T.; Pegel, S.; John, A.; Rentenberger, R.; Pötschke, P.
    Today polymer/carbon nanotube (CNT) composites can be found in sports equipment, cars, and electronic devices. The growth of old and new markets in this area has been stimulated by our increased understanding of relevant production and processing methods, as well as the considerable price reduction of industrial CNT grades. In particular, CNT based electrically conductive polymer composites (CPCs) offer a range of opportunities because of their unique property profile; they demonstrate low specific gravity in combination with relatively good mechanical properties and processability. The electrical conductivity of polymer/CNT composites results from a continuous filler network that can be affected by various external stimuli, such as temperature shifts, mechanical deformations, and the presence of gases and vapors or solvents. Accordingly, CNT based CPCs represent promising candidates for the design of smart components capable of integrated monitoring. In this article we focus on their use as leakage detectors for organic solvents.
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    Influence of molecular weight of polycation polydimethyldiallylammonium and carbon nanotube content on electric conductivity of layer-by-layer films
    (Amsterdam [u.a.] : Elsevier, 2022) Neuber, Sven; Sill, Annekatrin; Efthimiopoulos, Ilias; Nestler, Peter; Fricke, Katja; Helm, Christiane A.
    For biological and engineering applications, nm-thin films with high electrical conductivity and tunable sheet resistance are desirable. Multilayers of polydimethyldiallylammonium chloride (PDADMA) with two different molecular weights (322 and 44.3 kDa) and oxidized carbon nanotubes (CNTs) were constructed using the layer-by-layer technique. The surface coverage of the CNTs was monitored with a selected visible near infrared absorption peak. Both the film thickness and the surface coverage of the CNTs increased linearly with the number of CNT/PDADMA bilayers deposited (film thickness up to 80 nm). Atomic force microscopy images showed a predominantly surface-parallel orientation of CNTs. Ohmic behavior with constant electrical conductivity of each CNT/PDADMA film and conductivity up to 4 · 103 S/m was found. A change in PDADMA molecular weight by almost a factor of ten has no effect on the film thickness and electrical conductivity, only the film/air roughness is reduced. However, increasing CNT concentration in the deposition dispersion from 0.15 up to 0.25 mg/ml results in an increased thickness of a CNT/PDADMA bilayer (by a factor of three). The increased bilayer thickness is accompanied by a decreased electrical conductivity (by a factor of four). The decreased conductivity is attributed to the increased monomer/CNT ratio.