Micellization of a di-block copolymer in ethylene glycol and its utilization for suspension of carbonaceous nanostructures

Suspensions of carbonaceous nanoparticles (NPs) in ethylene glycol (EG) can be used as colloidal inks for additive manufacturing and nano-fluids for heat-transfer applications. While micellar solutions of surfactants are often used for suspension of the NPs in water, micellization of surfactants in EG is suppressed as compared to aqueous solutions and a well-defined critical micellization concentration (CMC) is often not observed. Unlike the surfactants, a di-block copolymer comprising a poly(ethylene glycol) monomethylether methacrylate (PEGMA) segment, 2-(diethylaminoethyl) methacrylate (DEAEMA) and butyl methacrylate (BMA), poly(O950)-b-(DEAEMA-co-BMA) was found to assemble into spherical micelles in EG. Surface tension measurements show a well-defined CMC that depends on the volume fraction of EG. Cryogenic transmission electron microscopy and dynamic light scattering show the presence of spherical micelles with a diameter that reduces with the volume fraction of EG. The micellar solutions were further used for suspending carbonaceous NPs of different geometry and characteristic dimensions: C₆₀ fullerenes, multi-walled carbon nanotubes, and nanodiamonds. The flow behavior of the suspensions exhibits a relatively low viscosity and mostly Newtonian behavior due to strong interaction between the NPs and the micelles. These suspensions may be used as colloidal inks for two-dimensional and three-dimensional printing.