Multifunctional Carbon Nanotube Composite Fibers

Abstract

Carbon nanotubes have been the focus of considerable research over the last decade. Because of their remarkable structural, mechanical, electrical, and thermal properties, [1] diverse applications have been envisioned. [2] Realization of these property advantages has been frustrated by material heterogeneity and impurities: catalyst and/or impurity carbons are present and as-produced nanotubes are mixtures of moderate bandgap semiconductors, very small bandgap semiconductors, and metallic conductors. Also, single-wall nanotubes (SWNTs) aggregate into bundles and larger, morerandom assemblies, and are difficult to uniformly disperse in melt or solution as either bundles or individual nanotubes. [3] Nanomanipulation techniques have been used for fabricating single-nanotube devices, such as sensors and field effect transistors, [4±6] but the probability of selecting the proper nanotubes needed for device function is low and these techniques are generally much too inefficient and unreliable to be used for making commercial practice. Nevertheless, strategies have been developed and practiced in the laboratory for fabricating carbon nanotube forests and other oriented nanotube assemblies (which can be used for field emitting devices), [7,8] self-standing carbon nanotube films (the so-called ªbucky-papersº), [9,10] and polymer and ceramic composites. [2,11±15] The addition of carbon nanotubes to polymeric or epoxy matrices results in composites with enhanced mechanical properties and electronic transport. [2,11,13] Composites of multiwall nanotubes (MWNTs) have been employed for initial practical applications, such as enabling electrostatic painting of automotive parts, and are of great interest for radio-frequency and electromagnetic shielding. [2,16] We have recently shown that intercalation of polymers in the porous structure of nanotube sheets increases Young's modulus, strength and toughness by factors of up to 3, 9, and 28, respectively. [17] The fabrication of carbon nanotube containing fibers is of special interest for mechanical and electronic textile applications. [18,19] Vigolo et al. developed an innovative coagulationbased fiber spinning technique: first, an aqueous dispersion of arc-discharge-produced single-wall carbon nanotubes (SWNTs) and surfactant (sodium dodecyl sulfate) is injected into a rotating bath of aqueous polyvinyl alcohol (PVA) solution, which serves as coagulant. [20±22] The nanotubes collapse during coagulation to form ribbon-like elastomeric gel-fibers. [23] Such gel-fibers are washed by immersion in successive water containers to remove excess PVA, and then dried by pulling from the water bath. The gel-fibers spun by this technique are difficult to disentangle and too weak to be easily handled. As a result, the produced dried fibers were typically short (some tens of centimeters long). Tensile strength and Young's modulus values of up to 230 MPa and 40 GPa, respectively, were reported for those dried SWNT/ PVA composite fibers. [20±22] This coagulation-based fiber spinning techniq...

Exploiting high quality PEDOT:PSS–SWNT composite formulations for wet-spinning multifunctional fibers

“…8,13,14 One of the most successful methods used to prepare SWNT-based composite fibers via wetspinning is to inject a surfactant stabilised SWNT dispersion into a bath that contains a polymer coagulant. [15][16][17][18][19][20][21] In this regard, a compromise in electrical conductivity, particularly for SWNTbased composite fibers that display excellent mechanical reinforcement, is observed. As an example, supertough PVA-SWNT fibers (prepared via the coagulation method), exhibit modulus, strength and toughness values as high as 80 GPa, 1.8 GPa and 570 J g À1 , respectively; 17 however, the electrical conductivity is low ($2.5 S cm À1 ) a direct result of the adverse effect of PVA (an insulator) on the overall electrical conductivity.…”

“…17,19 Although the removal of PVA via thermal annealing can enhance the electrical conductivity, the mechanical properties are severely compromised. 18,19 However, it has been shown that when the polymer host is inherently conducting such as polyaniline and polypyrrole, the addition of SWNT during the fiber spinning process provides significant benefits including, but not limited to, high electrical conductivity in contrast with an insulator polymer host such as PVA. [22][23][24][25] In a mechanically reinforced system, enhancement is generally achieved at low CNT loadings (typically 1 to 10% of SWNT).…”

DNA‐Wrapped Single‐Walled Carbon Nanotube Hybrid Fibers for supercapacitors and Artificial Muscles

“…While quite high actuation stresses were obtained in these thermally annealed CNT fibers, their low flexibility and high creep during charge and discharge were noted as significant problems. [5] Similarly, fibers spun without the aid of a polymer binder [1] produce high conductivities (140 S cm -1 after thermal annealing) and capacitances…”

Highly Conducting Carbon Nanotube/Polyethyleneimine Composite Fibers

“…Additionally, these SWNT fibers have been successfully utilized in the fabrication of electrochemical devices, such as electromechanical actuators [1,12] and supercapacitors. [10,11] However, unless the polymer is removed by pyrolysis (which degrades the mechanical properties of the fiber), performance of these electrochemical devices is limited by the low electrical conductivity of the nanotube/polymer composite fibers and degradation of mechanical stability when the PVA in these fibers is converted into an ionic conductor.…”