Removable Nonconjugated Polymers To Debundle and Disperse Carbon Nanotubes

Dispersion of Single-Walled Carbon Nanotubes by Aromatic Cyclic Schiff Bases via Non-Covalent Interactions

One of the challenging issues that hinders the application of single-walled carbon nanotubes (SWCNTs) is the poor solubility and the inevitable formation of bundles. Efforts still need to be made towards solving the problem. Herein, we report a non-covalent strategy to disperse aggregated SWCNTs by aromatic cyclic Schiff bases assisted by ultrasonic techniques. The aromatic cyclic Schiff base (OMM) was synthesized via Schiff base reactions, and the molecular structure was determined by ATR-FT-IR, solid-state 13C-NMR, and HRMS. Although the yielded product showed poor solubility in aqueous solution and organic solvents, it could interact with and disperse the aggregated SWCNTs in dimethyl formamide (DMF) under the condition of ultrasound. UV-vis-NIR, FL, Raman spectra, AFM, and TEM, along with computer simulations, provide evidence for the interactions between OMM molecules and SWCNTs and the dispersion thereof. The semiconductive (7,5), (8,6), (12,1), and (9,7)-SWCNTs expressed a preference for dissolution. The capability of dispersion is contributed by π-π, C-H·π, and lone pair (lp)·π interactions between OMM and SWCNTs based on the simulated results. The present non-covalent strategy could provide inspiration for preparing organic cyclic compounds as dispersants for SWCNTs and then facilitate their further utilization.

Carbon Nanotube-Directed 7 GPa Heterocyclic Aramid Fiber and Its Application in Artificial Muscles

Poly(p-phenylene-benzimidazole-terephthalamide) (PBIA) fibers with excellent mechanical properties are widely used in fields that require impact-resistant materials such as ballistic protection and aerospace. The introduction of heterocycles in polymer chains increases their flexibility and makes it easier to optimize the fiber structure. However, the inadequate orientation of polymer chains is one of the main reasons for the large difference between the measured and theoretical mechanical properties of PBIA fibers. Herein, carbon nanotubes (CNTs) are selected as an orientation seed. Their structural features allow CNTs to orient during the spinning process, which can induce an orderly arrangement of polymers and improve the orientation of the fiber microstructure. To ensure the complete 1D topology of long CNTs (≈10 µm), PBIA is used as an efficient dispersant to overcome dispersion challenges. The p-CNT/PBIA fibers (10 µm single-walled carbon nanotube 0.025 wt%) exhibit an increase of 22% in tensile strength and 23% in elongation, with a maximum tensile strength of 7.01 ± 0.31 GPa and a reinforcement efficiency of 893.6. The artificial muscle fabricated using CNT/PBIA fibers exhibits a 34.8% contraction and a 25% lifting of a 2 kg dumbbell, providing a promising paradigm for high-performance organic fibers as high-load smart actuators.

Electrostatic interaction-controlled dispersion of carbon nanotubes in a ternary composite for high-performance supercapacitors

Effective dispersion of carbon nanotubes (CNTs) is of great importance to achieve their intrinsic performance. Normally, it is believed that CNT dispersion is decided by interactions between CNTs and their dispersants, while other interactions are often neglected. Herein, three ionic surfactants, sodium dodecyl sulfate (SDS), dodecyl dimethyl betaine (BS-12) and cetyltrimethylammonium bromide (CTAB), are used to disperse CNTs in a ternary composite, i.e., poly(p-phenylenediamine)-phosphomolybdic acid@reduced graphene oxide (DMoG), respectively, leading to three different DMoGC composites. It has been found that the CNT dispersion in DMoGC was mainly controlled by electrostatic interactions between the surfactants and DMoG, which further exerted vital influences on the constitution, content, morphology, porous structure and supercapacitive performance of the DMoGC composites. Among the three surfactants, cationic CTAB showed the best CNT dispersion, while amphoteric BS-12 could hardly disperse CNTs in DMoGC, leading to DMoGC-CTAB with a 2 times larger specific surface area (152.3 m² g^-1) and 1.5 times higher specific capacitance (422 F g^-1) than those of DMoGC-(BS-12). Our study can provide valuable guidelines for selecting/designing effective dispersants to prepare multi-component composites containing uniformly dispersed CNTs.

Polystyrene Homopolymer Enhances Dispersion of MWCNTs Stabilized in Solution by a PS-b-P2VP Copolymer

Block copolymers (BCPs) have previously been identified as powerful multiwalled carbon nanotube (MWCNT) dispersants in solution. However, relatively high costs and limited dispersibility hinder the use of BCPs in large-scale practical applications. Partial replacement of BCP with a low-cost homopolymer (HP) offers a promising approach to produce cost-effective MWNCT dispersions. The effect of HP/BCP blends on MWNCT dispersion degree and stability has yet to be elucidated. In this work, we tested the hypothesis that HP-induced BCP micelle size variation affects MWCNT dispersibility. Here, blends of the BCP poly(styrene)-block-poly(2-vinylpyridine) and the HP polystyrene (PS) were applied to examine BCP micelles' size dependence on the MWCNT dispersion degree. Light microscopy results showed that using HP/BCP blends, MWCNT dispersion was enhanced by up to 263% compared to pure BCP at a constant weight ratio of BCP to MWCNTs. Based on the correlation of increased MWCNT dispersion degree with increased BCP micelle size, as revealed by dynamic light scattering, an MWCNT dispersion mechanism is proposed. The mechanism includes a rationale for the unexpected finding that HP PS swells the BCP micelle's PS corona in a good solvent for PS. Using HP to increase MWCNT dispersion is a promising approach with possible applications in the production of high-performance composite materials. This holds especially for formulations of practical relevance where often (BCP) dispersants are only one of many components in the material.

Highly Thermal Stable Phenolic Resin Based on Double-Decker-Shaped POSS Nanocomposites for Supercapacitors

In this study we incorporated various amounts of a double-decker silsesquioxane (DDSQ) into phenolic/DDSQ hybrids, which we prepared from a bifunctionalized phenolic DDSQ derivative (DDSQ-4OH), phenol, and CH₂O under basic conditions (with DDSQ-4OH itself prepared through hydrosilylation of nadic anhydride with DDSQ and subsequent reaction with 4-aminophenol). We characterized these phenolic/DDSQ hybrids using Fourier transform infrared spectroscopy; ¹H, ¹³C, and ²⁹Si nuclear magnetic resonance spectroscopy; X-ray photoelectron spectroscopy (XPS); and thermogravimetric analysis. The thermal decomposition temperature and char yield both increased significantly upon increasing the DDSQ content, with the DDSQ units providing an inorganic protection layer on the phenolic surface, as confirmed through XPS analyses. We obtained carbon/DDSQ hybrids from the phenolic/DDSQ hybrids after thermal curing and calcination at 900 °C; these carbon/DDSQ hybrids displayed electrochemical properties superior to those of previously reported counterparts.