Conformational behavior of polymers adsorbed on nanotubes (original) (raw)
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Nanoscale ordering of polymer adsorbed on nanotubes
We study the interaction of a dilute solution of semiflexible polymers with a weakly attractive infinitely long cylinder (i.e., nanotube) using Monte Carlo simulation. Apart for bending stiffness of the polymer chains, the only interactions considered in our model are weakly attractive shortranged Lennard-Jones interactions between the monomers and with the surface. These nonspecific interactions are found to result in stable helical and multi-helical adsorbed conformations for semiflexible chains. Adsorption of these chains is found to occur in a sequential manner through tight wrapping of the polymer around the nanotube. Adsorption occurs quickly and is characterized by a sharp peak in the heat capacity. A second transition follows whereby opening and reorganization of the adsorbed chains into nearly perfect helices and multiple helices. Extension of the model to block and triblock copolymers reveals rich conformational behavior. These results are discussed on physical grounds and implications towards polymer-carbon nanotube composites are offered.
Molecular Dynamics Simulations of Flexible Polymer Chains Wrapping Single-Walled Carbon Nanotubes
The Journal of Physical Chemistry B, 2010
The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs) and polymer chains with flexible backbones in vacuo via molecular dynamics (MD) simulations. These simulations investigate whether the polymers prefer to wrap the SWCNT, what the molecular details of that interface are, and how the interfacial interaction is affected by the chemical composition and structure of the polymer. The simulations indicate that polymers with flexible backbones tend to wrap around the SWCNT, although not in any distinct conformation; no helical conformations were observed. PAN with the cyano side group showed a preference for transversing the length of the SWCNT rather than wrapping around its diameter, and the cyano group prefers to align parallel to the SWCNT surface. Flexible backbone polymers with bulky and aromatic side groups such as PS and PMMA prefer intrachain coiling rather than wrapping the SWCNT. Moment of inertia plots as a function of time quantify the interplay between intrachain coiling and adsorption to the SWCNT surface.
Conformational behavior of semi-flexible polymers confined to a cylindrical surface
Chemical Physics Letters, 2006
Uniform wrapping of a polymers around carbon nanotubes has been recently reported as a means to separate individual nanotubes from their natural bundled state. It has been suggested that polymers wrap the nanotubes in a helical manner due to various interactions, including p-stacking, hydrophobic and van der Waals. In this communication, we show that surface curvature plays an important role in stabilizing helical conformations. We use Monte Carlo simulations supported by simple thermodynamics arguments to reveal that semiflexible chains adopt ordered helical conformations at a narrow range of radii, depending only on the stiffness of the chain and cylinder radius.
Exploration of polymer conformational similarities in polymer-carbon nanotube interfaces
2010
Abstract We are using molecular simulations to investigate the interface between the polymer matrix and the carbon nanotube reinforcement, which is the key aspect of the bulk properties of nanocomposites. These simulations are typically analyzed with standard techniques like graphs and animations; however, existing methods are limited for certain exploratory tasks for analyzing the interfacial domains.
Molecular Dynamics Simulation Study on the Carbon Nanotube Interacting with a Polymer
Using molecular dynamics simulation method, we studied the carbon nanotube (CNT) non-covalently interacting with a polymer. As the polymer coiled around the CNT, the diameter of CNT deformed by more than 40% of its original value within 50 ps. By considering three different polymers, we conclude that the interaction between the CNT and polymer is governed by the number of repeating units in the polymer, not by the molecular weight of polymer.
The stability and dispersion of carbon nanotube-polymer solutions: A molecular dynamics study
SAGE journals - Journal of Industrial Textiles, 2017
Carbon nanotubes have been explored to increase the mechanical properties and electrical conductivity of polymeric fibers through compounding with polymer to be extruded into fibers. However, this route creates major challenges because carbon nanotubes have strong cohesion and tend to aggregate and precipitate due to their poor interfacial interaction with polymers. In this study, classical molecular dynamics simulations are used to predict and characterize carbon nanotubes-polymer interface mechanism in two different polymer matrices: polyvinyl butyral and polystyrene-co-glycidyl methacrylate. The dominated interface mechanisms are discovered to shed light on carbon nanotubes dispersion in solvent based systems and to explore the prerequisites for stabilized nanofluids. Our results showed that p-stacking interactions between aromatic groups and graphene surfaces of carbon nanotubes as in polystyrene-co-glycidyl methacrylate systems, play an important role in dispersion of carbon nano-tubes, whereas slight repulsions between carbon nanotubes and polyvinyl butyral chains lead to large morphological differences and carbon nanotubes bundles in many chain systems. Altogether, the results indicated that polymers with structures having strong interactions with the surfaces of carbon nanotubes through p-p interactions are more effective in dispersing carbon nanotubes and caused stabilized solutions in wet fiber processing.
Molecular mechanics of binding in carbon-nanotube–polymer composites
Journal of Materials Research, 2000
Nanoscale composites have been a technological dream for many years. Recently, increased interest has arisen in using carbon nanotubes as a filler for polymer composites, owing to their very small diameters on the order of 1 nm, very high aspect ratios of 1000 or more, and exceptional strength with Young's modulus of approximately 1 TPa. A key issue for realizing these composites is obtaining good interfacial adhesion between the phases. In this work, we used force-field based molecular mechanics calculations to determine binding energies and sliding frictional stresses between pristine carbon nanotubes and a range of polymer substrates, in an effort to understand the factors governing interfacial adhesion. The particular polymers studied were chosen to correspond to reported composites in the literature. We also examined polymer morphologies by performing energy-minimizations in a vacuum. Hydrogen bond interactions with the -bond network of pristine carbon nanotubes were found to bond most strongly to the surface, in the absence of chemically altered nanotubes. Surprisingly, we found that binding energies and frictional forces play only a minor role in determining the strength of the interface, but that helical polymer conformations are essential.
Mixtures of Single-Walled Carbon Nanotubes (SWNTs) and polymers play an important role in practical applications such as ultrastrong lightweight materials and organic solar cells. In present work, we studied the interaction between SWNTs and polymers including poly(3-hexythiophene) (P3HT), Poly(2-methoxy-5-(3-7-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV), and Poly[[[(2ethylhexyl)oxy]methoxy-1,4-phenylene]-1,2-ethenediyl] (MEH-PPV) by molecular dynamics (MD) simulation. For the first time, we use molecular dynamics simulation based on a reactive force field (ReaxFF) to study the interaction between polymers and SWNTs. Interaction energy between polymers and SWNTs was calculated. Morphology of polymers adsorbed to the surface of SWNTs was investigated by the radius of gyration (R g ). Influence of temperature, SWNT radius, and chirality on interfacial adhesion of SWNT-polymer and R g of the polymers were studied. Our results showed that the strongest interaction between the SWNTs and these polymers was observed first for P3HT, then MDMO-PPV, and finally MEH-PPV. We found that the interaction energy is influenced by the specific monomer structure of the polymers, SWNT radius, and chirality, but the influence of temperature is very weak. The temperature, radius, and chirality have not any important effect on the radius of gyration.
Utilizing polymers for shaping the interfacial behavior of carbon nanotubes
Soft Matter, 2006
A major obstacle for utilization of carbon nanotubes is their tendency to bundle and pack into ropes that further entangle into networks, rendering the tubes insoluble in aqueous and organic liquids, and thus almost un-processable. As was shown recently, physically adsorbed block-copolymers may be used for exfoliating and dispersing carbon nanotubes in aqueous and organic media. In this approach entropic repulsion among polymeric layers attached to CNT induce steric repulsion among the polymer-decorated tubes. The tube-polymer interactions are relatively weak, do not depend on the detailed chemistry of the interface and their range is tuned by the molecular weight and density of the polymeric layers, rather than by the chemical composition of the monomers. Combining theoretical modeling and experimental studies we demonstrate that this approach may be used for engineering the interfacial behavior of carbon nanotubes in a variety of systems.
Journal of Physical Chemistry B, 2002
Production of stable polymer-nanotube composites depends on good wetting interaction between polymer and nanotube, which is polymer specific, and depends in particular on chain conformation. In this paper, we examine this interaction for a conjugated, semiconducting polymer by a range of microscopic and spectroscopic techniques, to gain a greater understanding of the binding. Several interesting effects are observed, including an order to the interaction between the polymer and nanotube, the tendency of defects in the nanotube structure to nucleate crystal growth, and substantial changes in the spectroscopic behavior of the polymer due to the effect of the nanotubes on polymer conformation. This is substantiated by computational modeling, which demonstrates that these conformational modifications are due to the interaction with the nanotubes.