Coating Mechanisms of Single-Walled Carbon Nanotube by Linear Polyether Surfactants: Insights from Computer Simulations

Abstract

ABSTRACT.The non-covalent coating of carbon-based nanomaterials, such as carbon nanotubes, has important applications in nanotechnology and nanomedicine. The molecular modeling of this process can clarify its mechanism and provide a tool for the design of novel materials. In this paper, the coating mechanism of single-walled carbon nanotubes (SWCNT) in aqueous solutions by 1,2 -dimethoxyethane oxide (DME), 1,2 -dimethoxypropane oxide (DMP), polyethylene oxide (PEO), polypropylene oxide (PPO) pentamers, and L64 triblock copolymer chains have been studied using molecular dynamics (MD) simulations. The results suggest a preferential binding to the SWCNT surface of the DMP molecules with respect to DME mainly driven by their difference in hydrophobicy. For the longer pentamers, it depends by the chain conformation. PPO isomers with radius of gyration larger than PEO pentamers bind more tightly than those with more compact conformation. In the case, of the L64 triblock copolymer, the coating of the SWCNT surface produce a shell of PPO blocks with the PEO chains protruding into bulk water as expected from the so-called non-wrapping binding mechanism of SWCNT. In addition, polymer coating, qualitative agreement with experimental evidences on the poor capability of the L64 to disperse SWCNT, do not prevent the formation of CNT aggregates.

Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity

“…The reason for this is plausibly the restriction imposed on molecular motions in the PPO block by its surface attachment. Strong anchoring of PPO blocks has been a feature observed in explicit molecular simulations of the adsorption of Pluronics to CNTs. , …”

“…Therefore, several dispersion methodologies have been devised, particularly in water. , Among those methodologies, the physical adsorption of dispersant molecules on the nanotube surface is often preferred because it (in contrast to chemical functionalization ) preserves the chemical and structural integrity of the nanotube. Thus far, several types of dispersantsusually amphiphilic molecules such as surfactants, − synthetic polymers, − proteins, − and DNA − have been used to exfoliate and stabilize CNTs in aqueous solvents. The adsorption of these dispersants onto the CNT surface is mainly driven by hydrophobic interactions , or π-stacking. , Further, electrostatic and/or steric repulsions between the surface-covered nanotubes provide the necessary kinetic stability of the obtained colloidal dispersion.…”

Molecular Simulations of PEGylated Biomolecules, Liposomes, and Nanoparticles for Drug Delivery Applications

“…Aslan et al compares density profiles of PEGylated lipids adsorbed onto isolated and bundled CNTs, which helps explain their different extents of antimicrobial activity [205]. Sarukhanyan et al [206] and Han et al [207] simulated CNTs interacting with various polymers, showing the effect of polymer hydrophobicity on the CNT-polymer conformation and interparticle dispersion. Maatta et al found the dependence of CNT dispersion on PEG length and CNT diameter [208].…”

Molecular dynamics simulations of adsorption of long pyrene-PEG chains on athin carbon nanotube

“…On the other hand, solvent polarity was shown to affect polymer adsorption on CNTs by altering polymer flexibility and the strength of nonbonded interactions [14]. MD simulations also provided important details on the interaction between CNTs and various polymeric systems, such as pyrene-attached polyethylene chains [14], branched PPOpolyethylene oxide segments [15], different polyether surfactants [16], polyamide-66 [17], lipid-PEG chains [18], and different flexible polymers [19,20].…”