Nanolatex architectonics: Influence of cationic charge density and size on their adsorption onto surfaces with a 2D...

It is theoretically predicted and hypothesized that the charge density and size of spherical nanoparticles are the key factors for their adsorption onto oppositely charged surfaces. It is also hypothesized that the morphology and charge of the surface are of great importance. In-plane 2D (silica) or a volumetric 3D (regenerated TEMPO-oxidized cellulose model surfaces) distribution of charged groups is expected to influence charge compensation and, thus, the adsorption behavior.

In this work, self-stabilized nanolatexes with a range of cationic charge densities and sizes were synthesized through reversible addition - fragmentation chain-transfer (RAFT) polymerization coupled with polymerization-induced self-assembly (PISA). Their adsorption onto silica and anionic cellulose model surfaces was investigated using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D).

Experiments and theory agree and show that the size of the nanolatex and the difference in charge density compared to the substrate determine the charge compensation and, thus, the surface coverage. Highly charged or large nanolatexes overcompensate the surface charge of non-porous substrates leading to a significant repulsive zone where other particles cannot adsorb. For porous substrates like cellulose, the vertical distribution of charged groups in the 3D volume prevents overcompensation and thus increases the adsorption. This systematic study investigates the isolated effect of surface charge and size and paves the way for on-demand particles specifically designed for a surface with particular characteristics.