Functional Coatings Optimization Through Colloidal Assembly

Achieving control over the distribution of inorganic nanoparticles across the thickness of latex nanocomposite films is one of the largest challenges to develop waterborne functional coatings. Here, we harness the size segregation that occurs during the drying of binary colloidal blends to drive zinc oxide or silica nanoparticles to the top surface of the coatings.[1] The chosen systems are highly relevant for antibacterial and abrasion resistant coatings, respectively. For high enough inorganic volume fraction, the nanoparticles assemble in superstructures at the top of the film whose height is heavily dependent on the evaporation rate used. In the case of ZnO composites, a slower evaporation rate leads to taller superstructures and a strongest antibacterial efficiency against E. coli. Based on our experiments and Brownian dynamics simulations, we establish a film formation model which explains the formation of superstructures and the final film architecture. Moreover, we demonstrate how a ternary film containing additional small latex particles results in improved surface stability and abrasion resistance compared with a binary film.[2] Our work provides a method to produce waterborne coatings with enhanced abrasion resistance and antibacterial activity as well as valuable insights into the mechanisms behind the formation of colloidal superstructures.<br/>References<br/>[1] Y. Dong et al. ACS Appl. Polym. Mater. 2020, 2, 626-635.<br/>[2] J. Tinkler et al. Journal of Colloid and Interface Science 2021, 581, 729-740.