Switching of surface composition and morphology of binary polymer brushes in response to changes in solvent selectivity, heating above glass transition temperatures, and contact with a rubbery stamp was studied. The binary brushes: polystyrene/poly(2-vinyl pyridine) (PS/P2VP), poly(styrene-co-2,3,4,5,6-pentafluorostyrene)/poly(methyl (meth)acrylate) (PSF/P(M)MA), and PS/PMMA were synthesized via two-step surface-initiated radical polymerization. Wetting experiments show that switching of brushes? surface composition upon exposure to solvents of various thermodynamic quality occurs faster than in 6 s. It takes longer time (5-10 min), if rate of solvent diffusion into the brush film is low. Discontinuous switching of surface composition of binary brushes is found upon exposure to binary solvents with gradually changed selectivity. X-ray Photoelectron Spectroscopy (XPS) shows quantitatively that the top brush layer (1) is dominated by respective favourite polymers after exposure to solvents of opposite selectivity and (2) comprises both brush constituents in almost symmetric ratio after exposure to non-selective solvents. Morphologies of binary brushes obtained after exposure to the solvents were studied with Atomic Force Microscopy (AFM). Local top layer composition was sensed with X-ray Photoemission Electron Microscopy (XPEEM). The morphologies are relevant to the particular solvents, reproducible, and independent on previous solvents. Phase segregation beneath the brush top layers was visualized with plasma etching. Qualitative agreement of the experimentally observed morphologies and predicted with self-consistent field theory is found. Enrichment of a binary brush top layer with the polymer providing lower surface energy takes place after annealing. Perpendicular segregation of binary brush constituents was sensed with XPEEM on perpendicular walls of imprinted elevations after wet microcontact printing.

Capillary trapping plays a central role in the geological storage of CO2, oil recovery, and water soil infiltration. The key aim of this study is to investigate the impact of surface properties (wettability, roughness, heterogeneous mineral composition) on the dynamics of quasi-static fluid displacement process and capillary trapping efficiency in porous medium. We concluded that for homogeneous wet smooth glass beads surfaces, a transition in fluid displacement pattern occurs from a compact (for θ < 90°; imbibition process) to a fractal front-pattern (for θ > 90°; drainage process) leading to a crossover in capillary trapping efficiency from zero to maximum. The impact of surface roughness on capillary trapping efficiency was also studied, and an opposite trends in terms of wettability dependency was observed. Rough natural sands surfaces depicts a non-monotonous wettability dependency, i.e. a transition from maximal trapping (for θ < 90°) to no-trapping occurs (at θ = 90°), followed by an increase to medium trapping (for θ > 90°). For a fractional-wet media, the percolating cluster of hydrophobic sediments (connected hydrophobic pathways) characterize the fluid displacement pattern and trapping efficiency.