Selective Intercalation of Polymers in Carbon Nanotubes

Abstract

A room-temperature, open-air method is devised to selectively intercalate relatively low-molecular-weight polymers (approximately 10-100 kDa) from dilute, volatile solutions into open-end, as-grown, wettable carbon nanotubes with 50-100 nm diameters. The method relies on a novel self-sustained diffusion mechanism driving polymers from dilute volatile solutions into carbon nanotubes and concentrating them there. Relatively low-molecular-weight polymers, such as poly(ethylene oxide) (PEO, 600 kDa) and poly(caprolactone) (PCL, 80 kDa), were encapsulated in graphitic nanotubes as confirmed by transmission electron microscopy, which revealed morphologies characteristic of mixtures in nanoconfinements affected by intermolecular forces. Whereas relatively small, flexible polymer molecules can conform to enter these nanotubes, larger macromolecules (approximately 1000 kDa) remain outside. The selective nature of this process is useful for filling nanotubes with polymers and could also be valuable in capping nanotubes.

Hollow Micro/Nanomaterials with Multilevel Interior Structures

“…Owing to the intrinsic hollow properties of carbon nanotubes (CNTs), Yarin and co-workers found that a low-molecular-weight polymer solution could enter into CNTs and form segmented or foamed inner structures. [133] They utilized a kind of open-ended wettable CNT as target. When the CNTs were immersed in a dilute solution of low-molecular-weight polymer, the polymer will enter into the CNTs and concentrate in the CNTs driven by a self-sustained diffusion mechanism.…”

Carbon Nanotubes as Containers

“…Relatively, low molecular weight polymers, such as poly(ethylene oxide) (PEO, 600 kDa) and poly(caprolactone) (PCL, 80 kDa), were encapsulated in MWNTs [59] ( Table 12.2). TEM images reveal foam and peapod-like patterns of the dried polymer in the nanotube channels.…”

Fabrication and Characterization of Ultrahigh‐Volume‐ Fraction Aligned Carbon Nanotube–Polymer Composites

“…In other cases, CNT forest microfeatures (e.g., a pillar of square cross-section) having aspect ratios close to 1 are densified by the solvent to create higher-volume-fraction microfeatures. [31,40] Capillarity-driven patterning is well reviewed [32,41,42] and the degree of wetting and densification are noted to be a function of the contact (or wetting) angle of the liquid with the CNTs, the liquid's viscosity, and CNT characteristics (diameter, volume fraction). Solvent-induced densification was also explored in this work using isopropyl alcohol, and the resulting forests were highly contracted, irregular, and contained micrometer-scale cells as observed by others.…”