Polymerization from the Surface of Single-Walled Carbon Nanotubes − Preparation and Characterization of Nanocomposites

Synthesis of Green and Red-Emitting Polymethyl Methacrylate Composites Grafted from ZnAl2O4:Mn-Bonded GO via Surface-Initiated Atom Transfer Radical Polymerization

A novel dual green and red-emitting photoluminescent polymer composite ZnAl₂O₄:Mn-bonded GO/polymethyl methacrylate (PMMA) was synthesized in a single-step reaction by surface-initiated atom transfer radical polymerization (SI-ATRP). The polymer chain was surface-initiated from the ZnAl₂O₄:Mn/GO, and the final products have a homogenous photoluminescent property from ZnAl₂O₄:Mn and better mechanical properties strengthened by graphene oxide (GO). The morphologies of ZnAl₂O₄:Mn/GO and the polymer composites were verified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction analysis (XRD) revealed the two valence states of Mn (Mn²⁺, Mn⁴⁺) existing in the ZnAl₂O₄ host lattice, while Fourier-transform infrared spectroscopy (FTIR) spectra proved the transference of the active group, C-Br, from the initiator to the monomer during the polymerization. Gel permeation chromatography (GPC) shows the narrow dispersity of polymer composites fabricated through SI-ATRP. The SEM and FTIR results show the successful ‘graft’ of the polymer chains from the surface of ZnAl₂O₄:Mn/GO. The dual green and red-emitting polymer composites were synthesized, confirmed by the photoluminescence (PL) and photoluminescence excitation (PLE) results.

Development and Characterization of Integrated Nano-Sensors for Organic Residues and pH Field Detection

Meeting global water quality standards is a real challenge to ensure that food crops and livestock are fit for consumption, as well as for human health in general. A major hurdle affecting the detection of pollutants in water reservoirs is the lapse of time between the sampling moment and the availability of the laboratory-based results. Here, we report the preparation, characterization, and performance assessment of an innovative sensor for the rapid detection of organic residue levels and pH in water samples. The sensor is based on carbonaceous nanomaterials (CNMs) coated with an intrinsically conductive polymer, polyaniline (PANI). Inverse emulsion polymerizations of aniline in the presence of carbon nanotubes (CNTs) or graphene were prepared and confirmed by thermogravimetric analysis and high-resolution scanning electron microscopy. Aminophenol and phenol were used as proxies for organic residue detection. The PANI/CNM nanocomposites were used to fabricate thin-film sensors. Of all the CNMs, the smallest limit of detection (LOD) was achieved for multi-walled CNT (MWCNT) with a LOD of 9.6 ppb for aminophenol and a very high linearity of 0.997, with an average sensitivity of 2.3 kΩ/pH at an acid pH. This high sensor performance can be attributed to the high homogeneity of the PANI coating on the MWCNT surface.

Polymer-functionalization of carbon nanotube by in situ conventional and controlled radical polymerizations

Functionalization of carbon nanotube (CNT) with polymers has drawn much attention due to its wide range of applications. Polymer-functionalized CNT could exhibit variety of properties, such as responsivity to environmental stimuli, ability of complexation with metal ions, increased dispersibility in different solvents, higher compatibility with polymer matrix, etc. Chemical and physical methods have been developed for the preparation of polymer-functionalized CNT. Polymer chains are chemically bonded to the CNT edge or surface in the chemical methods, which results in highly stable CNT/polymer composites. "Grafting to", "grafting from", and "grafting through" methods are the most common chemical methods for polymer-functionalization of CNT. In "grafting to" method, pre-fabricated polymer chains are coupled with the either functionalized or non-functionalized CNT. In "grafting from" and "grafting through" methods, CNT is functionalized by polymers simultaneously synthesized by in situ polymerization methods. Conventional free radical polymerization (FRP) and also controlled radical polymerization (CRP) are the most promising methods for in situ tethering of polymer brushes onto the surface of CNT due to their control over the grafting density, thickness, and functionality of the polymer brushes. The main focus of this review is on the synthesis of polymer-functionalized CNT via both the "grafting from" and "grafting through" methods on the basis of FRP and CRP routs, which is commonly known as in situ polymerizations. Finally, the most important challenges and applications of the in situ polymer grafting methods are discussed, which could be interesting for the future works.

Water-Based Lubricants: Development, Properties, and Performances

Water-based lubricants (WBLs) have been at the forefront of recent research, due to the abundant availability of water at a low cost. However, in metallic tribo-systems, WBLs often exhibit poor performance compared to petroleum-based lubricants. Research and development indicate that nano-additives improve the lubrication performance of water. Some of these additives could be categorized as solid nanoparticles, ionic liquids, and bio-based oils. These additives improve the tribological properties and help to reduce friction, wear, and corrosion. This review explored different water-based lubricant additives and summarized their properties and performances. Viscosity, density, wettability, and solubility are discussed to determine the viability of using water-based nano-lubricants compared to petroleum-based lubricants for reducing friction and wear in machining. Water-based liquid lubricants also have environmental benefits over petroleum-based lubricants. Further research is needed to understand and optimize water-based lubrication for tribological systems completely.

Chitosan/Silver Nanoparticle/Graphene Oxide Nanocomposites with Multi-Drug Release, Antimicrobial, and Photothermal Conversion Functions

In this work, we designed and fabricated a multifunctional nanocomposite system that consists of chitosan, raspberry-like silver nanoparticles, and graphene oxide. The room temperature atmospheric pressure microplasma (RT-APM) process provides a rapid, facile, and environmentally-friendly method for introducing silver nanoparticles into the composite system. Our composite can achieve a pH controlled single and/or dual drug release. Under pH 7.4 for methyl blue loaded on chitosan, the drug release profile features a burst release during the first 10 h, followed by a more stabilized release of 70-80% after 40-50 h. For fluorescein sodium loaded on graphene oxide, the drug release only reached 45% towards the end of 240 h. When the composite acted as a dual drug release system, the interaction of fluorescein sodium and methyl blue slowed down the methyl blue release rate. Under pH 4, both single and dual drug systems showed a much higher release rate. In addition, our composite system demonstrated strong antibacterial abilities against E. coli and S. aureus, as well as an excellent photothermal conversion effect under irradiation of near infrared lasers. The photothermal conversion efficiency can be controlled by the laser power. These unique functionalities of our nanocomposite point to its potential application in multiple areas, such as multimodal therapeutics in healthcare, water treatment, and anti-microbials, among others.

Ultrasonically Induced Polymerization and Polymer Grafting in the Presence of Carbonaceous Nanoparticles

Nanotechnology refers to technologies using at least one nanometric dimension. Most advances have been in the field of nanomaterials used in research and industry. The vast potential of polymeric nanocomposites for advanced materials and applications such as hybrid nanocomposites with customized electrical conductivity, anti-bacterial, anti-viral, and anti-fog properties have attracted considerable attention. The number of studies on the preparation of nanocomposites in the presence of carbon materials, i.e., carbon nanotubes (CNTs) and graphene, has intensified over the last decade with the growing interest in their outstanding synergic properties. However, the functionality of such nanocomposites depends on overcoming three key challenges: (a) the breakdown of nanoparticle agglomerates; (b) the attachment of functional materials to the nanoparticle surfaces; and (c) the fine dispersion of functional nanoparticles within the polymeric matrices. Ultrasonic polymerization and grafting in the presence of nanoparticles is an innovative solution that can meet these three challenges simultaneously. These chemical reactions are less well known and only a few research groups have dealt with them to date. This review focuses on two main pathways to the design of ultrasonically induced carbon-based nanocomposites: the covalent approach which is based on the chemical interactions between the carbon fillers and the matrix, and the non-covalent approach which is based on the physical interactions.

Carbon Nanotubes in Biomedicine

Nowadays, biomaterials have become a crucial element in numerous biomedical, preclinical, and clinical applications. The use of nanoparticles entails a great potential in these fields mainly because of the high ratio of surface atoms that modify the physicochemical properties and increases the chemical reactivity. Among them, carbon nanotubes (CNTs) have emerged as a powerful tool to improve biomedical approaches in the management of numerous diseases. CNTs have an excellent ability to penetrate cell membranes, and the sp² hybridization of all carbons enables their functionalization with almost every biomolecule or compound, allowing them to target cells and deliver drugs under the appropriate environmental stimuli. Besides, in the new promising field of artificial biomaterial generation, nanotubes are studied as the load in nanocomposite materials, improving their mechanical and electrical properties, or even for direct use as scaffolds in body tissue manufacturing. Nevertheless, despite their beneficial contributions, some major concerns need to be solved to boost the clinical development of CNTs, including poor solubility in water, low biodegradability and dispersivity, and toxicity problems associated with CNTs' interaction with biomolecules in tissues and organs, including the possible effects in the proteome and genome. This review performs a wide literature analysis to present the main and latest advances in the optimal design and characterization of carbon nanotubes with biomedical applications, and their capacities in different areas of preclinical research.

Layer-by-Layer Assembly of Clay-Carbon Nanotube Hybrid Superstructures

Much of the research effort concerning layered materials is directed toward their use as building blocks for the development of hybrid nanostructures with well-defined dimensions and behavior. Here, we report the fabrication through layer-by-layer deposition and intercalation chemistry of a new type of clay-based hybrid film, where functionalized carbon nanotubes are sandwiched between nanometer-sized smectite clay platelets. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized in a single step with phenol groups, via 1,3-dipolar cycloaddition, to allow for stable dispersion in polar solvents. For the production of hybrid thin films, a bottom-up approach combining self-assembly with Langmuir-Schaefer deposition was applied. Smectite clay nanoplatelets act as a structure-directing interface and reaction media for grafting functionalized carbon nanotubes in a bidimensional array, allowing for a controllable layer-by-layer growth at a nanoscale. Hybrid clay/SWCNT multilayer films deposited on various substrates were characterized by X-ray reflectivity, Raman, and X-ray photoelectron spectroscopies, as well as atomic force microscopy.

A Simple Method for Anchoring Silver and Copper Nanoparticles on Single Wall Carbon Nanotubes

Single walled carbon nanotubes (SWCNT) were functionalized using the 1,3-dipolar cycloaddition reaction of an azomethine ylide under solvent-free conditions, a one-pot procedure that yields pyrrolidine type of groups at the nanotubes surface. The functionalized SWCNT were further decorated with Ag and Cu nanoparticles by reduction of the corresponding metal salts in dimethylformamide. The extensive reduction of silver from its nitrate was observed, as well as the partial reduction of copper from its acetate. X-ray photoelectron spectroscopy (XPS) confirmed the functionalization of SWCNT with pyrrolidine that provided anchoring sites for the metal nanoparticles. Metal nanoparticles (NP) were formed at the surface of the organically functionalized SWCNT in higher yields as compared to the same procedure carried out with pristine SWCNT. This was observed using scanning electron microscopy (SEM) and quantified by XPS. Raman spectroscopy demonstrated that functionalization and metal decoration of the SWCNT did not induce structural damage to the SWCNT.

The Structure and Properties of Polyacrylonitrile Nascent Composite Fibers with Grafted Multi Walled Carbon Nanotubes Prepared by Wet Spinning Method

Polyacrylonitrile (PAN) grafted amino-functionalized multi walled carbon nanotubes (amino-MWCNTs) were synthesized by in situ polymerization under aqueous solvent. The grafted MWCNT/PAN nascent composite fibers were prepared by the wet spinning method. Fourier transform infrared spectroscopy and Raman spectroscopy indicated that the amino-MWCNTs and PAN macromolecular chains had interfacial interactions and formed chemical bonds. The grafting content of the PAN polymer on the amino-MWCNTs was up to 73.2% by thermo gravimetric analysis. The incorporation of the grafted MWCNTs improved the degree of crystallization and crystal size of PAN nascent fibers, and changed the thermal properties during exothermic processing in an air atmosphere. Morphology analysis and testing of mechanical properties showed that the grafted MWCNT/PAN nascent composite fibers with a more uniform diameter distribution and larger diameter had higher tensile strength and tensile modulus than the control PAN nascent fibers.

Anchoring conductive polymeric monomers on single-walled carbon nanotubes: towards covalently linked nanocomposites

Chemical functionalization with conductive polymeric monomers on carbon nanotubes carried out by a straightforward method.

Free volume, gas permeation, and proton conductivity in MIL-101-SO3H/Nafion composite membranes

The influence of free volume size on the gas permeability of MIL-101-SO₃H/Nafion composite membranes is closely related to the size of the particular gas molecules.

Depleting Depletion: Maintaining Single-Walled Carbon Nanotube Dispersions after Graft-To Polymer Functionalization

Grafting polymers onto single-walled carbon nanotubes (SWCNTs) usefully alters properties but does not typically yield stable, solvated species directly. Despite the expectation of steric stabilization, a damaging (re)dispersion step is usually necessary. Here, poly(vinyl acetate)s (PVAc's) of varying molecular weights are grafted to individualized, reduced SWCNTs at different concentrations to examine the extent of reaction and degree of solvation. The use of higher polymer concentrations leads to an increase in grafting ratio (weight fraction of grafted polymer relative to the SWCNT framework), approaching the limit of random sequentially adsorbed Flory "mushrooms" on the surface. However, at higher polymer concentrations, a larger percentage of SWCNTs precipitate during the reaction; an effect which is more significant for larger weight polymers. The precipitation is attributed to depletion interactions generated by ungrafted homopolymer overcoming Coulombic repulsion of adjacent like-charged SWCNTs; a simple model is proposed. Larger polymers and greater degrees of functionalization favor stable solvation, but larger and more concentrated homopolymers increase depletion aggregation. By using low concentrations (25 μM) of larger molecular weight PVAc (10 kDa), up to 65% of grafted SWCNTs were retained in solution (at 65 μg mL^-1) directly after the reaction.

Estimation of degree of polymerization of poly-acrylonitrile-grafted carbon nanotubes using Guinier plot of small angle x-ray scattering

Small angle x-ray scattering (SAXS) was used to estimate the degree of polymerization of polymer-grafted carbon nanotubes (CNTs) synthesized using a 'grafting from' method. This analysis characterizes the grafted polymer chains without cleaving them from CNTs, and provides reliable data that can complement conventional methods such as thermogravimetric analysis or transmittance electron microscopy. Acrylonitrile was polymerized from the surface of the CNTs by using redox initiation to produce poly-acrylonitrile-grafted CNTs (PAN-CNTs). Polymerization time and the initiation rate were varied to control the degree of polymerization. Radius of gyration (R _g ) of PAN-CNTs was determined using the Guinier plot obtained from SAXS solution analysis. The results showed consistent values according to the polymerization condition, up to a maximum R _g  = 125.70 Å whereas that of pristine CNTs was 99.23 Å. The dispersibility of PAN-CNTs in N,N-dimethylformamide was tested using ultraviolet-visible-near infrared spectroscopy and was confirmed to increase as the degree of polymerization increased. This analysis will be helpful to estimate the degree of polymerization of any polymer-grafted CNTs synthesized using the 'grafting from' method and to fabricate polymer/CNT composite materials.

Humidity- and light-driven actuators based on carbon nanotube-coated paper and polymer composite

Multi-responsive actuators driven by different stimuli (e.g. light, humidity, electricity) have attracted intense attention recently for the advantages of being used in various environments and show enormous actuation. In this work, we propose humidity- and light-driven actuators based on carbon nanotube (CNT)-coated paper and a biaxially oriented polypropylene (BOPP) composite. The CNT-paper/BOPP actuator shows large bending actuation when driven by humidity change (curvature of 1.2 cm-1) and near infrared (NIR) light irradiation (curvature up to 1.6 cm-1). The great actuation performances outperform most other paper-based actuators. Finally, a smart gripper, of which the initial opening width can be enlarged, is fabricated on the basis of the CNT-paper/BOPP actuators. By utilizing the bidirectional bending motion of the actuator, the opening width of the gripper can increase to a width that is 4 times larger than its initial width, so as to grasp a large object. The gripper is also able to raise and move an object that is 20 times heavier than one actuator of the gripper. We assume that this new type of actuator has great potential in artificial muscle, soft robotics and biomimetic applications.

Enhancement in Proton Conductivity and Thermal Stability in Nafion Membranes Induced by Incorporation of Sulfonated Carbon Nanotubes

Proton exchange membrane fuel cell (PEMFC) is one of the most promising green power sources, in which perfluorinated sulfonic acid ionomer-based membranes (e.g., Nafion) are widely used. However, the widespread application of PEMFCs is greatly limited by the sharp degradation in electrochemical properties of the proton exchange membranes under high temperature and low humidity conditions. In this work, the high-performance sulfonated carbon nanotubes/Nafion composite membranes (Su-CNTs/Nafion) for the PEMFCs were prepared and the mechanism of the microstructures on the macroscopic properties of membranes was intensively studied. Microstructure evolution in Nafion membranes during water uptake was investigated by positron annihilation lifetime spectroscopy, and results strongly showed that the Su-CNTs or CNTs in Nafion composite membranes significantly reinforced Nafion matrices, which influenced the development of ionic-water clusters in them. Proton conductivities in Su-CNTs/Nafion composite membranes were remarkably enhanced due to the mass formation of proton-conducting pathways (water channels) along the Su-CNTs. In particular, these pathways along Su-CNTs in Su-CNTs/Nafion membranes interconnected the isolated ionic-water clusters at low humidity and resulted in less tortuosity of the water channel network for proton transportation at high humidity. At a high temperature of 135 °C, Su-CNTs/Nafion membranes maintained high proton conductivity because the reinforcement of Su-CNTs on Nafion matrices reduced the evaporation of water molecules from membranes as well as the hydrophilic Su-CNTs were helpful for binding water molecules.

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

This paper provides an overview of recent advances in research on the interfacial characteristics of carbon nanotube–polymer nanocomposites. The state of knowledge about the chemical functionalization of carbon nanotubes as well as the interaction at the interface between the carbon nanotube and the polymer matrix is presented. The primary focus of this paper is on identifying the fundamental relationship between nanocomposite properties and interfacial characteristics. The progress, remaining challenges, and future directions of research are discussed. The latest developments of both microscopy and scattering techniques are reviewed, and their respective strengths and limitations are briefly discussed. The main methods available for the chemical functionalization of carbon nanotubes are summarized, and particular interest is given to evaluation of their advantages and disadvantages. The critical issues related to the interaction at the interface are discussed, and the important techniques for improving the properties of carbon nanotube–polymer nanocomposites are introduced. Additionally, the mechanism responsible for the interfacial interaction at the molecular level is briefly described. Furthermore, the mechanical, electrical, and thermal properties of the nanocomposites are discussed separately, and their influencing factors are briefly introduced. Finally, the current challenges and opportunities for efficiently translating the remarkable properties of carbon nanotubes to polymer matrices are summarized in the hopes of facilitating the development of this emerging area. Potential topics of oncoming focus are highlighted, and several suggestions concerning future research needs are also presented.

The state of research on the characteristics at the interface in polymer nanocomposites is reviewed. Special emphasis is placed on the recent advances in the fundamental relationship between interfacial characteristics and nanocomposite properties.

Epoxy composites with functionalized molybdenum disulfide nanoplatelet additives

As a typical layered inorganic analogue of graphene, molybdenum disulfide (MoS₂) has gained intensive attention and become a research hotspot due to its unique two dimensional nanostructure and excellent properties. The enhancement in the thermal and mechanical properties of polymer/inorganic nanosheet composites depends strongly on their interfacial interaction. In this study, we exfoliated bulk MoS₂ into nanosheets which were subsequently functionalized using 3-mercaptopropyltriethoxysilane. The functionalized MoS₂ (f-MoS₂) were dispersed in epoxy polymers at loading fractions of up to 1% by weight via ultrasonication and three roll mills. We characterized the tensile, fracture and adhesive properties of the composite and show that f-MoS₂ nanoplatelets are highly effective at enhancing the mechanical properties of the epoxy at very low nanofiller loading fractions (0.1–0.7% by weight). Our results show the potential of functionalized 2D sheets of transition metal dichalcogenides as reinforcing additives in polymeric composites. The results indicate that the glass transition temperature increases significantly for the lower weight fraction composites, from 135 °C for the baseline (unfilled) epoxy to 146 °C at 0.7% f-MoS₂ loading. The apparent shear strength at 120 °C increases significantly for the lower weight fraction composites, from 13.8 MPa for the baseline (unfilled) epoxy to 24.9 MPa at 0.7% f-MoS₂ loading.

As a typical layered inorganic analogue of graphene, molybdenum disulfide (MoS₂) has gained intensive attention and become a research hotspot due to its unique two dimensional nanostructure and excellent properties.

Preparation of Hydrophilic Encapsulated Carbon Nanotubes with Polymer Brushes and Its Application in Composite Hydrogels

Carbon nanotubes can be used as promising reinforcement materials to improve the mechanical properties of hydrogels, but their poor dispersibility in aqueous solution severely limits their application in preparation of composite hydrogels. Therefore, to develop method for modification of carbon nanotubes is still highly desired. In this paper, a facile approach for preparation of the hydrophilic carbon nanotube was reported. The encapsulated multiwalled carbon nanotubes (E-CNT-PAA) with cross-linked shell structure were obatined through the self-assembly of the amphipathic azide diblock copolymers poly(acrylic acid)-b-poly(4-vinylbenzyl azide-co-styrene) (PAA-b-(PVBA-co-PS)), and the cross-linking of inside azide groups under UV irradiation. The encapsulated MWCNT was characterized by FT-IR, Raman and TEM. It was demonstrated that the dispersibility of the hydrophilic encapsulated MWCNTs was related to the length of the poly(acrylic acid) brushes. Subsequently, thermal-responsive composite hydrogels (PNIPAM/E-CNT-PAA) were prepared by in situ polymerization of N-isopropylacrylamide (NIPAM) in the solution of dispersed E-CNT-PAA. The results showed that the composite hydrogels possessed high mechanical properties compared to the pure PNIPAM hydrogel. The tensile strength and elongation of the composite hydrogels were highly dependent on the content of the modified MWCNTs. The composite hydrogels with 0.46 wt % MWCNTs exhibited tensile strength of 97.7 kPa and elongation of 465%, which were at least 3.5× higher than those of the PNIPAM hydrogel. Moreover, the composite hydrogels displayed significant and reversible stimuli-responsiveness.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Polypyrrole Nanotubes and Their Carbonized Analogs: Synthesis, Characterization, Gas Sensing Properties

Polypyrrole (PPy) in globular form and as nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the absence and presence of methyl orange, respectively. They were subsequently converted to nitrogen-containing carbons at 650 °C in an inert atmosphere. The course of carbonization was followed by thermogravimetric analysis and the accompanying changes in molecular structure by Fourier Transform Infrared and Raman spectroscopies. Both the original and carbonized materials have been tested in sensing of polar and non-polar organic vapors. The resistivity of sensing element using globular PPy was too high and only nanotubular PPy could be used. The sensitivity of the PPy nanotubes to ethanol vapors was nearly on the same level as that of their carbonized analogs (i.e., ~18% and 24%, respectively). Surprisingly, there was a high sensitivity of PPy nanotubes to the n-heptane vapors (~110%), while that of their carbonized analog remained at ~20%. The recovery process was significantly faster for carbonized PPy nanotubes (in order of seconds) compared with 10 s of seconds for original nanotubes, respectively, due to higher specific surface area after carbonization.

NR/SBR composites reinforced with organically functionalized MWCNTs: simultaneous improvement of tensile strength and elongation and enhanced thermal stability

Butyl acrylate-α-methyl methacrylate-glycidyl methacrylate (BA-MMA-GMA) terpolymer was successfully grafted onto carbon nanotubes (CNTs) via a facile grafting functionalization approach, affording an organically functionalized multiwalled CNTs (O-MWCNTs), which show improved mechanical and thermal properties in natural rubber/styrene-butadiene rubber (NR/SBR) composites. Under optimized conditions, the result of elongation at break of NR/SBR composites combined with 1.5 parts per hundred rubber (phr) O-MWCNTs is 450% compared to 376% of pristine NR/SBR composites, which is proportional to tensile strength due to the mixed O-MWCNTs in the rubber matrix. Transmission electron microscopy study shows that O-MWCNTs (1.5 phr) can disperse uniformly in NR/SBR/O-MWCNT composites. A scanning electron microscopy study on the fractured surface morphology of the optimized composites reveals that a BA-MMA-GMA terpolymer can interact with the rubber matrix strongly. The decreased height of the maximum tanδ peak shows that O-MWCNTs can reduce the heat buildup and damping capability of NR/SBR/O-MWCNT composites. The largest enhancement observed in the thermal degradation curves of composites is, for the first time, about 70°C, which can be attributed to enhanced interfacial interaction between MWCNTs and the rubber matrix.

Thermoresponsive Ultrathin Membranes with Precisely Tuned Nanopores for High-Flux Separation

With the growing demand for small- and large-scale bioprocesses, advanced membranes with high energy efficiency are highly required. However, conventional polymer-based membranes often have to sacrifice selectivity for permeability. In this work, we report the fabrication of a thermoresponsive composite ultrathin membrane with precisely controlled nanopores for high-throughput separation. The composite membrane is made by grafting a PEG analogue thermoresponsive copolymer onto an ultrathin single-wall carbon nanotubes (SWCNTs) membrane via π-π interaction with no use of the common "grafting from" synthesis approach. The composite membrane exhibits ultrahigh water permeation flux as high as 6430 L m(-2) h(-1) at 40 °C, and more importantly, the pore size of the membrane could be finely adjusted by utilizing the thermoresponsive property of the grafted copolymer. With the temperature changing below and above the lower critical solution temperature (LCST) of the copolymer, the effective pore size of the membrane can be tuned precisely between approximately 12 and 14 nm, which could be applied to effectively separate materials with very small size differences through size sieving.

Recent advances in organic–inorganic well-defined hybrid polymers using controlled living radical polymerization techniques

Controlled living radical polymerizations, such as ATRP and RAFT polymerization, could be utilized for the preparation of well-defined organic–inorganic hybrid polymers based on POSS, PDMS, silica nanoparticles, graphene, CNTs and fullerene.