Molecular-Level Engineering of Adhesion in Carbon Nanomaterial Interfaces

Abstract

Weak interfilament van der Waals interactions are potentially a significant roadblock in the development of carbon nanotube- (CNT-) and graphene-based nanocomposites. Chemical functionalization is envisioned as a means of introducing stronger intermolecular interactions at nanoscale interfaces, which in turn could enhance composite strength. This paper reports measurements of the adhesive energy of CNT-graphite interfaces functionalized with various coverages of arylpropionic acid. Peeling experiments conducted in situ in a scanning electron microscope show significantly larger adhesive energies compared to previously obtained measurements for unfunctionalized surfaces (Roenbeck et al. ACS Nano 2014, 8 (1), 124-138). Surprisingly, however, the adhesive energies are significantly higher when both surfaces have intermediate coverages than when one surface is densely functionalized. Atomistic simulations reveal a novel functional group interdiffusion mechanism, which arises for intermediate coverages in the presence of water. This interdiffusion is not observed when one surface is densely functionalized, resulting in energy trends that correlate with those observed in experiments. This unique intermolecular interaction mechanism, revealed through the integrated experimental-computational approach presented here, provides significant insights for use in the development of next-generation nanocomposites.

Nanoscale Mechanical Characterization of 1D and 2D Materials with Application to Nanocomposites

“…In these measurements, one end of a CNT is attached to the Zhang et al (2014) tip of an AFM cantilever which is brought away from the surface until the CNT detached itself from the surface in order to measure adhesion. This has demonstrated CNTs functionalized to exhibit high adhesion toward graphene-based nanocomposites (Roenbeck et al 2015). In addition to peeling, the shear interactions between adjacent CNTs within CNT bundles can also be measured using a similar technique in situ SEM.…”

Atomistic modeling of graphene/hexagonal boron nitride polymer nanocomposites: a review

“…Still, after a decade of research on polymer‐based nanocomposites, researchers are working on developing techniques that can overcome the shortcomings associated with the manufacturing of these nanocomposites. As the atomistic structure of graphene contains uniformly dispersed carbon atoms, their molecular level interactions with polymers include weak van‐der Waals (vdW) force, hydrophobic–hydrophobic interaction and π–π stacking . Moreover, the planar shape and strong π–π interactions among the different sheets of graphene force them to reaggregate .…”

“…This leads to a shaky interface between graphene and polymers, and possibility of agglomeration at higher volume fractions of graphene. In order to address the issue of agglomeration, chemically functionalizing the surface of GS with the groups that are able to trigger the polymerization process (bonded interactions) is considered as a possible solution . In this course of action, functionalized sheets are dispersed into the monomer units, and then the polymer chains directly develop from sheet surface, ensuring a better dispersion and good interaction between them …”

“…As the atomistic structure of graphene contains uniformly dispersed carbon atoms, their molecular level interactions with polymers include weak van-der Waals (vdW) force, hydrophobic-hydrophobic interaction and π-π stacking. 37,128 Moreover, the planar shape and strong π-π interactions among the different sheets of graphene force them to reaggregate. 129 This leads to a shaky interface between graphene and polymers, and possibility of agglomeration at higher volume fractions of graphene.…”

“…In order to address the issue of agglomeration, chemically functionalizing the surface of GS with the groups that are able to trigger the polymerization process (bonded interactions) is considered as a possible solution. 128,129 In this course of action, functionalized sheets are dispersed into the monomer units, and then the polymer chains directly develop from sheet surface, ensuring a better dispersion and good interaction between them. 82 In contrast to carbon-based materials, h-BN nanostructure utilizes very limited number of chemical reactions to realize the effective surface modifications.…”