Adsorption of Pluronic Surfactants in Alkylene Carbonates on Silica

Adsorption of triblock Pluronic surfactants bearing poly(ethylene oxide) (PEO) chains of different lengths, L-62 (5 EO groups on each end), L-64 (13 EO groups on each end), and F-68 (79 EO groups on each end), on silica has been characterized using atomic force microscopy (AFM). The solvent used herein was a mixture of ethylene carbonate (EC) and propylene carbonate (PC). The three Pluronic surfactants were dissolved in the mixed solvent, with the PEO chain acting as a solvophilic group and the poly(propylene oxide) (PPO) chain acting as a solvophobic group. The approaching force curve measurements for the three Pluronics (at 10 mmol dm–3) revealed repulsive forces from an apparent separation of 20–30 nm. The most solvophilic Pluronic surfactant with the longest PEO chain (F-68) showed continuously increasing repulsive interaction with decreasing separation. The Milner–Witten–Cates (MWC) theory described the repulsive force curve data of F-68, suggesting that F-68 forms a polymer brush on the silica surfa...