Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints

Abstract

Water-based processing of graphene—typically considered as physicochemically incompatible with water in the macroscale—emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp 2 -carbon nanoallotropes. Indeed, nanomaterials hidden under the common “graphene” signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene–polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the “growth-from” polymerization of l -DOPA ( l -3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10–20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s –1 and a low yield stress τ 0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene–PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq –1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

The Origin of Amphipathic Nature of Short and Thin Pristine Carbon Nanotubes—Fully Recyclable 1D Water‐in‐Oil Emulsion Stabilizers

“…Note that this coating has better characteristics than coatings based on pristine graphene flakes. [ 33 ]…”

“…Note that this coating has better characteristics than coatings based on pristine graphene flakes. [33] www.advmatinterfaces.de Information). Among the seven systems studied, we identified three systems (17, 26, and 46 wt.% of n-decane) in which the probability of finding oil molecules above the CNT sidewall is higher than finding them next to the CNT edges, whereas water molecules are preferentially located in the direct vicinity of CNT edges.…”

“…G) W/O emulsion stabilized by purified MWCNTs toward manufacturing of the flexible electroconductive coating (resistance 89.2 Ω, surface resistivity 44.6 Ω sq −1). Note that this coating has better characteristics than coatings based on pristine graphene flakes [33].…”

Covalent functionalization of 1D and 2D sp2-carbon nanoallotropes – twelve years of progress (2011–2023)

“…One of the important alternatives is to process CNTs (or graphene) as Pickering emulsions in systems of hydrophilic and hydrophobic solvents. 45,46 On the other hand, the troublesome agglomeration of CNTs has launched an immense number of studies on their covalent functionalization.…”

“…Generally, defect sites contribute to the poor electrical and mechanical properties of graphene materials. 46 Additionally, the size of graphene nanoplatelets is often constrained, while numerous synthetic approaches produce multilayered graphene nanosheets. The Raman spectra of graphene nanoplatelets contain distinct G-bands at 1580 cm −1 , D-bands at 1350 cm −1 , and a 2D-band at 2700 cm −1 , just like other 2D carbon nanoallotropes.…”