The Conformation and Adsorption Density of Block Copolymers on the Surface of Carbon Nanotubes in an Organic Medium

The unique properties of Carbon nanotubes (CNTs) make them perfect candidates for many potential applications, such as composite materials. However, their strong tendency to agglomerate, makes the quality of their dispersion in the processing liquid crucial for obtaining the desired distribution and functionality in the final composite.

The dispersion of CNTs by physical adsorption of polymers, through specific interfacial interactions, hinders their aggregation, allows them to retain their functional properties and improves the chemical compatibility between the CNTs and the matrix in composites, thus strengthening the interface.

Stable homogeneous dispersions of multi-walled carbon nanotubes (MWNTs) in N,N-dimethyl formamide (DMF) were achieved by physical modification of the MWNT surface using several block copolymers, with various molecular weights and chemical structures.

In order to characterize the morphology of the block copolymers on the Surface of the MWNTs, direct imaging via cryogenic transmission electron microscopy (cryoTEM) was combined with small angle neutron scattering (SANS) measurements. While cryoTEM imaging allowed qualitative evaluation of the CNT distribution, SANS contrast variation measurements provided detailed structural information on the MWNT/copolymer hybrid, with particular emphasis on the conformation and adsorption density of the copolymers on the MWNT surface.

Similar dispersions with single-walled carbon nanotubes (SWNTs) or with Graphene instead of MWNTs were also examined, in order to evaluate the influence of tube dimensions and surface curvature on the adsorption properties.