Effects of hydrophilic unit and its distribution on interfacial binding between single-walled carbon nanotubes, vinyl pyrrolidone and vinyl acetate copolymers

Abstract

In this work, a molecular dynamic (MD) simulation method was employed to study the interfacial binding between the single-walled carbon nanotubes (SWCNTs) and some polymers and copolymers. The polymers studied include poly(vinyl pyrrolidone) as hydrophilic and poly(vinyl acetate) as hydrophobic polymers and also copolymers consisting of a series of vinyl pyrrolidone and vinyl acetate copolymers with different homogeneities in the backbone. The copolymers investigated have different structures and include alternative, diblock and triblock copolymers. This study has computed the intermolecular interaction energies between SWCNTs and polymers/copolymers in order to assess the effects of compositional heterogeneity on the interfacial binding between SWCNTs and polymers/copolymers. Also, the morphology of polymers/copolymers adsorbed to the surface of nanotubes has been studied. The obtained results showed that the intermolecular interactions in the simulated systems are strongly influenced by the monomer sequence distribution of hydrophilic and hydrophobic monomers in copolymers. The different values of intermolecular interaction energy for copolymers with identical numbers of hydrophilic and hydrophobic monomers but with different distributions suggest that an efficient load transfer through the interface between nanotube and copolymers is highly dependent on compositional heterogeneity of copolymers. Furthermore, we obtained the plots of the radial distribution function and the radius of gyration in order to study the effects of compositional heterogeneity on behavior of the studied nanocomposites. The results of the radial distribution function and the radius of gyration are in agreement with the findings of interfacial binding between SWCNTs and polymers/copolymers.