Annealing and layer formation of nanoparticles especially the application of colloidal inks applied to porous materials is crucial for functional coatings and printing. Our goal is to distinguish and quantify the differences in structure formation during annealing of the deposited colloidal inks on a) a porous material and b) a solid non- porous material. Therefore, a layer of cellulose nano fibers (CNFs) – so-called nanopaper – and silicon wafers were used as porous and non-porous materials, respectively. For the layer formation of colloids on top of the CNF thin film, the colloid-CNF and the colloid-colloid interactions in a liquid state play a significant role. To meet this challenge, we used novel colloidal inks consisting of poly-butylmethacrylate (PBMA) and poly-sobrerolmethacrylate (PSobMA) in an aqueous dispersion. These colloidal inks are based on a cationically hydrophilic block chain extended and a hydrophobic block forming core-shell nanoparticles with different morphologies. This provided us with the advantage of tailoring their surface and core chemistry on-demand. To study the real time structural and morphological changes during deposition and annealing process, we utilized grazing incidence small-angle X-ray scattering (GISAXS). In addition, for a better understanding of the drying process, we investigated the interaction between the CNF and colloids in aqueous dispersion by small-angle neutron scattering (SANS). We demonstrate that the colloidal dispersions enter the CNF layer, the mixture of solvent and colloids remain on top of the CNF surface, which leads to a very complex drying and annealing process, and the cationically charged nanolatexes successfully adsorb into cellulose surfaces. In addition, the structure and morphology of both CNF- and colloidal layers can be influenced by exceeding the glass transition temperature of the colloids.

Colloidal layer formation and imbibition of colloidal inks on and in thin cellulose films

ACS Spring 2022

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