Toward Reuseable Particle-Based Materials: Solvency-Controlled Selective Recovery of Distinct Polymer-Coated Nanoparticles from Model and Device Surfaces

Selective recuperation of nanoparticles from device interfaces is a necessary condition for establishing circular economy approaches for a range of devices ranging from sensing to light harvesting in photovoltaics. We present a solution-based approach, which demonstrates "orthogonal" re-dispersion of different nanoparticle types by exposure to green solvent mixtures. Our approach is centered around co-nonsolvency-induced volume-phase transitions in polymer brushes at flat and nanoparticulate surfaces, which serve to control the adhesion force between the nanoparticles and the macroscopic surface depending on the composition of the mixed solvent. By employing polymers that enter the co-nonsolvency regime at markedly different solvent compositions-here poly(N-isopropylacrylamide) and poly(2-methacryloyloxyethyl phosphorylcholine)-it becomes possible to selectively release one sort of nanoparticles, while another particle sort remains adhered. This phenomenon was demonstrated in washing tests on silicon model substrates and real device surfaces, and it was mechanistically rationalized by coarse-grained molecular dynamics simulations. Our work thereby serves as an essential step toward disassembly strategies for particle-based materials and devices that aim at re-using the nanoparticulate building blocks.