The formation of water channels greatly improves the overall ion transport rate through densified carbon nanotube arrays.

Ion transport plays an important role in solar-to-electricity conversion, drug delivery, and a variety of biological processes. Carbon nanotube (CNT) is a promising material as an ion transporter in the applications of the mimicking of natural ion channels, desalination, and energy harvesting. Here, we demonstrate a unique, enhanced ion transport through a vertically aligned multiwall CNT membrane after the application of an electric potential across CNT membranes. Interestingly, electrowetting arising from the application of an electric potential is critical for the enhancement of overall ion transport rate through CNT membranes. The wettability of a liquid with high surface tension on the interior channel walls of CNTs increases during an electric potential treatment and promotes the formation of water channels in CNTs. The formation of water channels in CNTs induces an increase in overall ion diffusion through CNT membranes. This phenomenon is also related to a decrease in the charge transfer resistance of CNTs (R) after an electric potential is applied. Correspondingly, the enhanced ion flow rate gives rise to an enhancement in the capacitive performance of CNT based membranes. Our observations might have profound impact on the development of CNT based energy storage devices as well as artificial ion channels.

The glass-transition behaviors of the nanocomposites comprised of poly(methyl methacrylate) (PMMA) and multiwalled carbon nanotubes (MWCNTs) were investigated. The average glass-transition temperatures (T g ) of PMMA/CNT nanocomposites strongly depend on the nanocomposite structure or the orientation of CNTs in composites. The coexistence of the polymer layer with high mobility at the free surface of PMMA coating on CNT sidewalls and low-mobility PMMA chains in the interfacial zone locally in contact with CNTs leads to the local heterogeneity of polymer dynamics. In the PMMA/CNT nanocomposite with vertically aligned and densified CNT arrays (DCNTA), the PMMA chains with reduced dynamics in the interfacial zone near CNT sidewalls dominate the average T g and lead to an increase in T g . In the PMMA/CNT nanocomposite with randomly distributed CNTs (RCNT), a polymer layer with high mobility at the free surface of PMMA coating on CNT sidewalls causes a decrease in average T g . The PMMA/CNT nanocomposites also exhibit a broader glass transition.

We investigate the effect of the presence of vertically aligned multiwalled carbon nanotubes (CNTs) on the orientation of poly(ethylene oxide) (PEO) lamellae and PEO crystallinity. The high alignment of carbon nanotubes acting as templates probably governs the orientation of PEO lamellae. This templating effect might result in the lamella planes of PEO crystals oriented along a direction parallel to the long axis of the nanotubes. The presence of aligned carbon nanotubes also gives rise to the decreases in PEO crystallinity, crystallization temperature, and melting temperature due to the perturbation of carbon nanotubes to the crystallization of PEO. These effects have significant implications for controlling the orientation of PEO lamellae and decreasing the crystallinity of PEO and thickness of PEO lamellae, which have significant impacts on ion transport in PEO/CNT composite and the capacitive performance of PEO/CNT composite. Both the decreased PEO crystallinity and the orientation of PEO lamellae along the long axes of vertically aligned CNTs give rise to the decrease in the charge transfer resistance, which is associated with the improvements in the ion transport and capacitive performance of PEO/CNT composite.

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