Assessing carbon nanotube arrangement in polystyrene matrix by magnetic susceptibility measurements

Abstract

Multi-wall carbon nanotubes filled with iron nanoparticles were combined with polystyrene to evaluate interface interactions and nanotube orientation in composite using magnetic susceptibility measurements. Iron-containing species were introduced into MWCNT cavities as the result of catalytic chemical vapor deposition synthesis using ferrocene as a catalyst source. Polystyrene loaded with certain quantity of MWCNTs was uniaxially stretched to provide the nanotube alignment. Magnetic susceptibility measurements performed in three perpendicular directions of magnetic field confirmed the alignment in the stretching direction. The composites showed a large diamagnetic response in a magnetic field perpendicular to the nanotube axis and low response in a parallel field. In a quantitative sense, anisotropy exceeds by more than an order of magnitude the effect expected from intrinsic susceptibility of nanotubes. Apparently, the graphitic nature of the nanotube lattice results in strong non-covalent interactions with uniaxially stretched polymer matrix, and aromatic rings as side groups of polystyrene align parallel to the nanotube surface, contributing to strong diamagnetism. As magnetic susceptibility is a penetrative but non-destructive type of measurement, it can successfully characterize both the alignment of onedimensional or two-dimensional carbon allotropies and the arrangement of the macromolecules around them, contributing to the optimal design and performance of nanocomposites.

The preparation of carbon nanofillers and their role on the performance of variable polymer nanocomposites

“…Advancements are being made to produce such nanocomposites; however, the challenges in the characterization of alignment of CNTS and matrix are ominous and complicated due to non-crystallinity of the materials, the elemental identity of the filler, and the hindrance from matrix prevents the use of diffraction and spectroscopic methods. Makarova et al came up with novel magnetic susceptibility measurements that offer critical insights pertaining to the orientation of CNTs and PS molecules [99]. The ability to make such measurements was by incorporation of ironbased nanoparticles in the nanotube cavity that act as anisotropic magnetic species.…”

High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates

“…Before the solvent evaporation step, it is likely that PS block interacts favorably with CNT walls by π–π stacking, , while epoxidized polyisoprene (ePI) block extends free into solution due to the favorable interaction with DGEBA, as expected from the similar solubility parameters (δ ePI = 20.3 MPa –1/2 ; δ DGEBA = 20.7 MPa –1/2 ) . On the basis of the previous argument, Figure A depicts a possible conformation for eSIS consisting of PS blocks wrapping CNT walls and ePI subchains generating a steric barrier that prevents CNT agglomeration, in a similar way as previously reported by Kang and Taton for a polystyrene- block -poly­(acrylic acid) BCP surrounding single-walled carbon nanotubes dispersed in water .…”

“…In this regard, AFM phase imaging revealed that epoxy/eSIS films prepared with toluene as solvent (without DT) results in smaller sphere-like nanostructures (Supporting Information), while when using DT as cosolvent the BCP renders short cylinder-like nanostructures, presumably due to the higher mobility of eSIS during the self-assembly stage (before the solvent evaporation step under vacuum) enabling nanodomain association/aggregation. Before the solvent evaporation step, it is likely that PS block interacts favorably with CNT walls by π−π stacking, 50,51 while epoxidized polyisoprene (ePI) block extends free into solution due to the favorable interaction with DGEBA, as expected from the similar solubility parameters (δ ePI = 20.3 MPa −1/2 ; δ DGEBA = 20.7 MPa −1/2 ). 18 On the basis of the previous argument, Figure 3A depicts a possible conformation for eSIS consisting of PS blocks wrapping CNT walls and ePI subchains generating a steric barrier that prevents CNT agglomeration, in a similar way as previously reported by Kang and Taton for a polystyreneblock-poly(acrylic acid) BCP surrounding single-walled carbon nanotubes dispersed in water.…”

Correlation between manufacturing processes and anisotropic magnetic and electromagnetic properties of carbon nanotube/polystyrene composites

“…rings are aligned perpendicular to it [32]. When the polystyrene is filled with the carbon nanotubes, its diamagnetic response changes not only quantitatively but also qualitatively.…”