Polymer Nanotubes Research Articles

Multi-functional and integrated actuators made with bio-inspired cobweb carbon nanotube–Polymer composites

Soft actuators have emerged as flexible platforms that can integrate many functional electronic devices to build intelligent electronic systems. The energy supply and wireless signal transmission of electronic systems of the multi-functional actuators are challenging research areas. Here, the idea of the functionalized and hierarchical design is proposed to construct the multi-functional and integrated actuators. Inspired by the structure of cobwebs, multi-functional carbon nanotube (CNT)-polymer composites with network structures are proposed and applied in multi-responsive actuators, supercapacitors, and electromagnetic interference (EMI) shielding devices. Two multi-functional and integrated actuators are highlighted to demonstrate the practical applications. One is a light-driven actuator integrated with an EMI shielding function, which can be used as an intelligent shielding curtain. The other is an electrical-driven actuator integrated with an energy storage function. Especially, the functions of actuation and energy storage can be simultaneously/independently used without interfering with each other. We provide comprehensive research from the material level (CNT-polymer composites) to the device level (actuators, supercapacitors, EMI shielding devices), and then to the system level (multi-functional actuators). We believe that the integration design of the multi-functional actuators will open up new avenues for the development of soft robotics, wireless signal transmission switch, and deformable supercapacitors.

Highly efficient of CO2/CH4 separation performance via the pebax membranes with multi-functional polymer nanotubes

Based on the one-dimensional tubular structure of halloysite nanotubes (HNTs), plant polyphenols and polyamines were used for in situ polymerization on the surface of HNTs to form amino-rich polymers, which were then removed as templates to synthesize polymer nanotubes. These nanotubes were then incorporated into a Pebax matrix to prepare mixed-matrix membranes (MMMs) for CO2/CH4 gas separation. The removal of the HNT template increased the lumen diameter of the filler and significantly improved its gas permeability. And the amino groups on the inner surface of the polymer nanotubes were exposed. Further, the number of CO2 reaction sites increased, which improved the reaction selectivity of CO2. In addition, the presence of amine groups on the inner and outer surfaces of the polymer nanotubes provided various transfer channels for CO2, which were conducive for CO2 gas transfer in the membrane. When the CC-PEINT content was 8 wt%, the CO2 permeability was 710 Barrer and CO2/CH4 selectivity was 60. The CO2 permeability and CO2/CH4 selectivity of the Pebax/CC-PEINTs membranes increased by 163% and 132%, respectively, compared with those of the pure Pebax membrane.

Application of a Synthetic Polymer Nanocomposite Latex in a Wellbore Cement Slurry for Gas Blockage Functions.

Commercial synthetic polymers are a professional approach to creating versatile new materials with high-performance classes. This research focuses on controlling gas migration within cement in the early stages of cement setting through a newly synthesized butadiene–carbon nanotube (CNT) polymer nanocomposite latex. The optimized cement in these experiments exhibits the inherited combination behavior from the flexible characteristics of the polymer matrix and the mechanical features from the carbon nanotubes. The feedback of the superelastic behavior of carbon nanotubes is indicated by a 75% increase in the modulus of elasticity and a 48% increase in the flexural strength in cementitious samples reinforced with the polymer nanocomposite latex. The improvement of surface tension by the polymer latex in the slurry and enough tensile strength during cement hydration have positive control and compensatory effects in early shrinkage and resistance to the development of fissures and cracks in the hardening cement. Optimized cement slurries containing polymer nanocomposite additives dramatically reduce the critical transfer time window to about 40 min for gelatinized cement, thereby reducing the risk of gas migration during the mentioned critical period for the cement slurry.

Ultra‐Sensitive and Quick‐Responsive Hybrid‐Supercapacitive Iontronic Pressure Sensor for Intuitive Electronics and Artificial Tactile Applications

AbstractRecent advances in supercapacitive pressure sensors based on iontronic film have a significant capacitive response and a low detection limit due to their large capacitance change resulting from electrical double layer (EDL) and these pressure sensors are used to detect a wide range of pressure with high resolution for various applications such as prosthesis, wearable devices, and robotics. Thus, the enhancements to the EDL capacitive response are significantly important challenges for advanced applications with outstanding performances. Herein, an ultra‐sensitive and quick‐responsive hybrid‐supercapacitive iontronic pressure sensor using a novel sensing mechanism and facile fabrication technique is reported to overcome the limitations of the existing iontronic pressure sensors. As a sensing material, conductive polymer and carbon nanotube are incorporated into the iontronic film, as pseudo‐ and EDL‐capacitive material, respectively. Moreover, vinyl silica nanoparticle (VSNP) is used to decrease the recovery time by making the iontronic film quick‐response. The developed hybrid‐supercapacitive pressure sensor exhibited an ultra‐high sensitivity of 301.5 kPa−1over a wide pressure range of up to 63.3 kPa along with a fast recovery time of ≈32 ms. It is believed that the proposed hybrid‐supercapacitive mechanism in iontronic film will significantly enhance the performance of conventional iontronic pressure sensors.

Substrate Modification for High‐Performance Thermoelectric Materials and Generators Based on Polymer and Carbon Nanotube Composite

AbstractPolymer and carbon nanotube composites have aroused extensive attention for thermoelectric materials owing to the combination of low thermal conductivity of polymer and high electrical conductivity of carbon nanotubes. Surface properties of the substrate are of great importance for the charge transport behaviors of semiconducting thin films, which are less explored in thermoelectric applications. Herein, self‐assembled monolayers (SAMs) are used to modify the substrate for thermoelectric polymer composites. The trifluoromethyl (CF3)‐terminated SAM is beneficial for an improved electrical conductivity; while the SAM with amino group is found to improve their Seebeck coefficient and decrease the electrical conductivity. As a result, polymer composites on CF3‐SAM‐modified substrate show a high room‐temperature power factor of 285 µW m−1 K−2 and a large output power of 2.36 µW for thermoelectric generator at a temperature gradient of 50 K. This work demonstrates that surface modification by SAMs is a promising strategy for improving performance of thermoelectric materials and devices.

Continuous wave THz imaging of multi-walled carbon nanotubes polymer composites

In this paper, the problem of creating homogeneous composites with on carbon nanotubes is described. To control the quality of the manufactured composites, a system of terahertz visualization of material inhomogeneity using a continuous radiation source is used. An increase in the homogeneity of the composite based on multi-walled carbon nanotubes with an increase in the time of ultrasonic processing during polymerization is noted. The advantages of THz imaging in comparison with optical microscopy are shown.

In English

The possibilities to enhance the properties of nanostructured surfaces are evaluated on “polymer-multiwall carbon nanotube” composites. Influence of sp3 hybridization bonds is investigated in composites derived from polypropylene, polyamide-6, polyamide-12 and polyvinyl chloride after adding CNTs to polymers. IR absorption of “polymer-CNTs” films exceeds that of polymer by 10-103 times in the entire measured spectral range. In addition, two-polar IR absorption are measured on composites with negative components at spectral positions of “D-band” and “2D-band” of sp3 hybridization. In this case, the greater oscillation amplitudes of C-C, CH2 and CH3 bonds correspond to a higher absorption at the vibration frequencies γω(CН) and γω(CH2). Two-polar oscillations of absorption with a negative component in the spectral band ranges “D” and “2D” of sp3 hybridization in nanotubes have been measured for the composites. Frequencies of 2D-band correspond to the second order frequencies of D-band. The intensity of 2D band increases with an increase in the concentration of defects. The absorption of light increases when the frequencies of local oscillations of surface bonds in carbon nanotubes correspond to the frequencies of slotted modes along the boundary of the “nanotube polymer” (surface polaritons). Two-polar oscillations have an ultra-small half width 0.4–0.6 cm–1, which indicates a strong interaction of surface polaritons with photons. Vertically polarized light along carbon nanotubes and horizontally polarized light of D and 2D bands resulted in light beams splitting, two-photon interference and realization of the quantum Hong-Ou-Mandel effect.

A Sequenced Study of Improved Dielectric Properties of Carbon Nanotubes and Metal Oxide-Reinforced Polymer Composites.

Polymers have gained attraction at the industrial level owing to their elastic and lightweight nature, as well as their astonishing mechanical and electrical applications. Their scope is limited due to their organic nature, which eventually leads to the degradation of their properties. The aim of this work was to produce polymer composites with finely dispersed metal oxide nanofillers and carbon nanotubes (CNTs) for the investigation of their charge-storage applications. This work reports the preparation of different polymeric composites with varying concentrations of metal oxide (MO) nanofillers and single-walled carbon nanotubes (SWCNTs). The successful synthesis of nanofillers (i.e., NiO and CuO) was carried out via the sonication and precipitation methods, respectively. After, the smooth and uniform polymeric composite thin films were prepared via the solution-casting methodology. Spectroscopy and diffraction techniques were used for the preliminary characterization. Scanning electron microscopy was used to check the dispersion of carbon nanotubes (CNTs) and MOs in the polymer matrix. The addition of nanofillers and carbon nanotubes (CNTs) tuned the bandgap, reduced the strain, and enhanced the elastic limit of the polymer. The addition of CNT enhanced the mechanical strength of the composite; however, it increased the conductivity, which was tuned by using metal oxides. By increasing the concentration of NiO and CuO from 2% to 6% bandgap of PVA, which is 5–6 eV reduced to 4.41 and 4.34 eV, Young’s moduli of up to 59 and 57.7 MPa, respectively, were achieved. Moreover, improved dielectric properties were achieved, which shows that the addition of metal oxide enhances the dielectric behavior of the material.

Confinement of Prussian Blue Analogs Boxes Inside Conducting Polymer Nanotubes Enables Significantly Enhanced Catalytic Performance for Water Treatment

AbstractTubular nanoreactor with unique void‐confinement effect has captured great attention for catalytic applications but is challenging in controllable fabrication and realizing a synergistically enhanced performance. Herein, a template polymerization‐guided synthetic strategy is presented to confine hollow Prussian blue analog boxes inside conducting polypyrrole nanotubes (H‐CoFe PBA@PPy NTs) as efficient peroxymonosulfate activator toward catalytic oxidation of toxic organic contaminants. This delicately designed H‐CoFe PBA@PPy NTs display a superior kinetic rate constant compared with the pristine CoFe PBA cubes (7.9 fold) and H‐CoFe PBA boxes (22.6 fold). Experimental evidence reveals that the generation of multiple reactive oxygen species in the nanotubes plays a vital role for the significantly enhanced catalytic efficiency for dye degradation. The superior catalytic performance is attributed to the intrinsic bimetallic CoFe PBA to provide abundant active sites, distinct nanotubular structure to concentrate the reactant molecules within a confined space, and excellent electron/mass transport property. This work presents new horizons for the design of high‐efficiency and stable catalysts with space confinement effects to promote future advanced water treatment technology.

Mechanical properties of carbon nanotube reinforced polyurethane matrix using computational method: a molecular dynamics study

The reinforcing nanostructures can be made up of nanoparticles, nanosheets or nanofibres such as carbon nanotubes (CNTs) and graphene nanosheets. To investigate the reinforce mechanism, the changes in mechanical behavior of CNT reinforced Polyurethane (PU) matrix with various chirality was studied using molecular dynamics (MD) method in current work. We used the DREIDING and Tersoff force-fields for simulation of the PU and CNT samples, respectively. To report the mechanical properties of pristine PU matrix and reinforced PU/CNT structure, some physical parameters such as interaction energy between polymer chains and nanotube atoms, ultimate strength, and Young’s modulus are calculated. MD outputs indicated inserting CNT with zigzag edge into pristine matrix enlarged the Young’s modulus by 17.10% and the ultimate strength by 25.69%. These results indicated the promising effect of CNT-based nanostructures on the mechanical properties of PU matrix.

Effect of microwave on mechanical properties of laser-sintered carbon nanotube polymer composites

ABSTRACT In this work, carbon nanotubes (CNT)/polyethersulfone (PES) polymer composites were prepared by selective laser sintering, and the effects of microwave treatment on mechanical properties and tensile fracture surfaces of the composites were investigated. The experimental results indicated that tensile strength and bending strength of the composites upon microwave treatment for 5–25 s were improved by 4–20.4% and by 4.5–47.7%, respectively. The tensile fracture surface morphology of the composites depended on the time length of microwave treatment. Upon microwave treatment, the fracture surface showed fewer pores and better interfacial bonding between adjacent polymer particles. The fracture mechanisms for the microwave-treated carbon nanotube/polymer composites prepared by selective laser sintering were discussed.

Polymeric Nanotubes as Drug Delivery Vectors─Comparison of Covalently and Supramolecularly Assembled Constructs

Rod-shaped nanoparticles have been identified as promising drug delivery candidates. In this report, the in vitro cell uptake and in vivo pharmacokinetic/bio-distribution behavior of molecular bottle-brush (BB) and cyclic peptide self-assembled nanotubes were studied in the size range of 36–41 nm in length. It was found that BB possessed the longest plasma circulation time (t1\\2 > 35 h), with the cyclic peptide system displaying an intermediate half-life (14.6 h), although still substantially elevated over a non-assembling linear control (2.7 h). The covalently bound BB underwent substantial distribution into the liver, whereas the cyclic peptide nanotube was able to mostly circumvent organ accumulation, highlighting the advantage of the inherent degradability of the cyclic peptide systems through their reversible aggregation of hydrogen bonding core units.

Halloysite nanotube and chitosan polymer composites: Physicochemical and drug delivery properties

Advancement in healthcare requires sophisticated and safe drug delivery systems. An ideal drug delivering system should be non-toxic, therapeutically inert, and be able to deliver a wide range of drugs. Here, we report halloysite nanotubes (HNTs) and its nanocomposite with chitosan for the delivery of diclofenac. The nanomaterials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). Also, water absorption studies, cytotoxicity studies, and in vitro diffusion studies were carried out to ascertain the behaviour of the nanomaterials. SEM confirmed tubular morphology of HNTs and suggest drug loading within nanotubes. Further, XRD diffraction patterns of diclofenac and HNTs in drug-loaded nanotubes and composites confirmed loading of drug in nanotubes at the first step of processing and encapsulation within composites in subsequent step. FTIR showed very few drug bands within drug loaded nanotubes and composite, confirming encapsulation of the drug. Nanocomposite films were found to sustain drug release for a longer duration. The drug sustaining phenomenon was confirmed via in vitro diffusion studies and water absorption studies. Cytotoxicity study performed by MTT assay suggests biocompatibility of HNTs nanomaterials. Overall, the studies imply that HNTs could be exploited as a biocompatible nanomaterials to deliver drugs that demand sustained therapeutic action.

Effect of aspect ratio on piezo-resistance properties of aligned multi-walled carbon nanotube polymer composites

Multi-walled carbon nanotubes (MWNTs) are actively used as reinforcing and electrical filler materials in composites owing to their superior electrical and mechanical performances. The electrical, mechanical, and piezoresistive performances of MWNT/polymer composites vary depending on the filler direction and aspect ratio (A/R). In this study, we fabricated MWNT/polymer composites with fillers aligned at different A/R. To prepare the aligned MWNT polymer composite with three different A/R, well dispersed MWNTs in the polymer matrix were applied continuous shear force in one direction by two-roll mill. Also, randomly oriented composites using same fillers were compared their mechanical, electrical, and piezoresistive properties to aligned composites. The aligned composite with the high A/R showed 6.03 times higher in elastic modulus and 17.4 times higher in electrical conductivity compared to the randomly oriented composite with the low A/R. The piezo-resistance, expressed as the maximum resistance change in tension, of the aligned composite with the low A/R had 84% higher than that of the randomly arrayed composite with the high A/R. In contrast to the enhancement of mechanical and electrical properties as the A/R rises and alignment occurs, the resistance in tension increases as the A/R decreases and the fillers are aligned. Thus, the influence of the filler alignment on the piezo-resistance properties of the composite is significant.

Carbon Nanotubes‐Based 3D Printing Ink for Multifunctional “Artificial Epidermis” with Long‐Term Environmental Stability

Abstract3D printing is a rapidly developing field because it has been widely used in the rapid design and manufacturing of flexible sensors to meet the needs of complex soft structures and devices. In this study, a composite hydrogel ink composed of polyvinyl alcohol, silk fibroin, conductive polymer, and carbon nanotubes is designed,and using 3D printing technology an “artificial epidermis” with long‐term environment stability and self‐healing ability is created. In addition, the “artificial epidermis” also has the multifunctional characteristics of sensing pressure, strain, temperature, and humidity. It has a wide pressure (0–165 kPa), strain (0–355%), temperature (−20–68 °C) and humidity (45–85%) sensing range and high sensitivity. While detecting the tiny movements of the human body, after self‐healing, the device can fully restore its sensing capabilities and perform accurate human monitoring. Furthermore, it can also monitor changes in temperature and humidity, distinguish between hot and cold water, and perform detection of water droplets. Customized 3D printing of flexible electronic devices has opened up new ways for the biological integration of various sensors in wearable electronic systems and the application of advanced bionic skin.

Poly(safranine T)-deep eutectic solvent/copper oxide nanoparticle-carbon nanotube nanocomposite modified electrode and its application to the simultaneous determination of hydroquinone and catechol

This work presents the combined use of safranine (SF) as a redox polymer and multiwalled carbon nanotubes (MWCNT)-copper oxide nanoparticles (CuO) in the development of a novel sensor for the simultaneous analysis of hydroquinone (HQ) and catechol (CAT). Electropolymerisation of SF was carried out in acid-doped ethaline deep eutectic solvent to prepare poly(safranine) (PSFEthaline) film electrodes with three different nanostructured architectures on pencil graphite electrodes (PGE) as electrode substrate. The polymerisation was done after nanomaterial surface modification to obtain PSFEthaline-HCl/MWCNT/PGE, PSFEthaline-HCl/CuO/PGE, and PSFEthaline-HCl/MWCNT-CuO/PGE. The synthesis, preparation, and characterisation of PSF film-coated electrodes were studied using cyclic voltammetry and electrochemical impedance spectroscopy to investigate the contribution of each nanomaterial on sensor performance. The best result for polymer film growth was obtained with PSF electrodeposited on MWCNT-CuO/PGE in HCl doped-ethaline. The analytical performance of the modified electrode was evaluated for electrochemical sensing of HQ and CAT by differential pulse voltammetry in aqueous Britton-Robinson buffer solution. Due to the combined effect of MWCNT-CuO nanocomposite film and PSF, the modified electrode sensor provided sensitive and selective detection of HQ and CAT with good peak separation. The simultaneousdetermination of HQ and CAT in both tap water and milk samples was successfully carried out to demonstrate the analytical applicability of the sensor. The sensor could be a promising analytical approach for monitoring the amount of HQ and CAT in real samples.

Supervised and unsupervised machine learning of structural phases of polymers adsorbed to nanowires.

We identify configurational phases and structural transitions in a polymer nanotube composite by means of machine learning. We employ various unsupervised dimensionality reduction methods, conventional neural networks, as well as the confusion method, an unsupervised neural-network-based approach. We find neural networks are able to reliably recognize all configurational phases that have been found previously in experiment and simulation. Furthermore, we locate the boundaries between configurational phases in a way that removes human intuition or bias. This could be done before only by relying on preconceived, ad hoc order parameters.

Electrochemical Sensing of Nitrite Ions Using Modified Electrode by Poly 1,8-Diaminonaphthalene/Functionalized Multi-Walled Carbon Nanotubes.

A novel electrochemical sensor based on conducting polymer and multi-walled carbon nanotubes was reported for the detection of nitrite ions (NO2 −). The hybrid material poly 1,8-Diaminonaphthalene (poly 1,8-DAN)/functionalized multi-walled carbon nanotubes (f-MWCNT) was prepared by using a simple electrochemical approach which is based on the deposition of functionalized multi-walled carbon nanotubes (f-MWCNT) on the surface of the electrode followed by the electropolymerization of 1,8-DAN using cyclic voltammetry. The morphology and the electro-catalytic properties of the obtained electrodes were investigated with Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS) showing an improvement of the electronic transfer due to the synergic effect between the proprieties of poly 1,8-DAN and f-MWCNT. Under the optimum experimental conditions, the poly 1,8-DAN/f-MWCNT/CPE exhibited excellent electro-catalytic activity towards nitrite detection. The nitrite anodic peak potential decreased by 210 mV compared to the bare carbon paste electrode. The calibration plot of nitrite detection was linear in the range of concentration from 300 to 6500 nM with a low detection limit of 75 nM.

Polymerizable channel-like stacks derived from cyclic tetrameric diacetylenes

A small series of cyclic diacetylenes has been synthesized and tested by scanning electron microscopy (SEM), single crystal X-ray diffraction, and atomic force microscopy (AFM) to examine their ability to form arrangements of discrete molecules in the solid state. Examining solid state structures clearly demonstrated propensity of diacetylene tetramers to form channel-like stacks. Remarkably, cyclotetradiyne DA-4 monomer tends to produce two types of nano-tubular motifs (i.e., the channel-like arrangement with solvent matrix inside and unprecedented flattened nano-tube incorporated no solvent guest molecules) which is indicative of the weak C–H/π interactions dominating and directing the stacking in such simplistic diacetylene cyclic systems. Noteworthy, DA-4 molecules may be crystallized from organic solvents into birefringent branchy patterns revealed by Polarized Optical Microscopy (POM) and twisted ribbons of both handedness as evidenced by SEM data. We hypothesize that all these secondary structures may arise from the bundling the individual stacks discovered by single crystal X-ray analysis. Overall, engineering the elongated motifs may open up new opportunities for the future applications such as a rational design of synthetic ion channels and carriers, synthesis of the covalent polymeric nanotubes, etc.

Electrical and Thermal Properties of Carbon Nanotube Polymer Composites with Various Aspect Ratios.

In response to the rising need for flexible and lightweight materials capable of efficient heat transport, many studies have been conducted to improve the thermal properties of polymers via nanofillers. Among the various nanofillers, carbon nanotubes (CNTs) are considered as the most promising, owing to their excellent thermal and electrical properties. Accordingly, CNT/polymer composites can be used as flexible and lightweight heat transfer materials, owing to their low density. In this study, we fabricated multi-walled CNT (MWCNT)/polymer composites with different aspect ratios to investigate their effects on electrical and thermal properties. Through a three-roll milling process, CNTs were uniformly dispersed in the polymer matrix to form a conductive network. Enhanced electrical and thermal properties were observed in MWCNT composite with a high aspect ratio as compared to those with a low aspect ratio. The thermal conductivity of composites obtained as a function of the filler content was also compared with the results of a theoretical prediction model.