Ephemeral Amphiphilic Polyamines that Evaporate When Triggered─Implications for the Fabrication of Electronic Inks

Without surfactants, nanomaterials tend to be aggregated in the liquid state. However, the presence of surfactants in the solid state can negatively impact the mechanical, electronic, and optical properties of the nanomaterial. Here, we have explored the design of an ephemeral surfactant, that is to say a surfactant, which is stable in solution but can be depolymerized in the solid phase and then be evaporated. The reaction of glyoxal with a 1,3-diamine leads to an unprecedented ladder polyamine (LPA), which depolymerizes into evaporable monomers as soon as it is in contact with acid. These LPA oligomers were found to be amphiphilic and could be used to stabilize a dispersion of polymer nanoparticles (NPs) in water. Once dipped in a slightly acidic solution, the dried polymer film was found to be devoid of the LPA surfactant. This concept was used to fabricate an electronic ink based on multiwalled carbon nanotubes (MWCNTs) whereby the LPA depolymerization was triggered by a photoacid generator. After applying the ink on a glass substrate, the conductivity of the MWCNT films was low, due to the charge transfer resistance created by the interfacial surfactant. Once exposed to light, the surfactant depolymerized and evaporated, and the film recovered its native conductivity. We envision that these ephemeral surfactants could become useful assets in the fabrication of electronic inks.