Study Of CTAB Adsorption Behavior In A Confined Solid/liquid Interface Via Admicellar Polymerization

A nano-pattern made by e-beam lithography on a silica surface masked with poly(methylmethacrylate)(PMMA, with a thickness of20nm and150nm)was used in this work to studyconfined adsorption behavior of CTAB. The pattern with straight trenches varied between50nm and2μm wide with silica (SiO2) at the bottom. Admicellar polymerization (AP) was usedto “solidify” the micelle structure to help to understand confinement effects on the adsorptionbehavior of CTAB by Atomic Force Microscope (AFM) images through the morphology ofpolypyrrole (PPy) after the mark was removed. The study found that:(1) PPy was hemispherical and randomly distributed on the silica surface in a noconfinement system. The average diameter and height the particles was57.7nm and23.4nm,respectively.(2) The depth and width of trench, the concentration of CTAB and Py monomer, andco-solvent can affect the adsorption behavior of CTAB.A、Confinement effect was observed when the trench size was narrowed to500nm andless, but not when the trench was2μm wide. For the trenches with150nm-depth, When thetrench width was large enough (>2μm), CTAB aggregates showed (hemi)spherical structureson SiO2surface while hemicylindricals assembled along the trench were found when thetrench width was less than50nm.B、For the trenches with a20nm-depth, no confinement effect was observed. All of thethe structures of PPy layers obtained in trenches were bilayers whatever the trench width was.C、The addition of the cosolvent not only changes the structure of the CTAB aggregatesbut also eliminates the size confinement effect. Thin film of PPy layers were obtained by theadding of cosolvent to the admicellar polymerization system. The trench size didn’t show anyinfluence on the PPy morphology.D、The concentration of CTAB will affect emulsifying effect of Py which lead todifferent morphologies of PPy in the confinement and5mM is the best concentration for Py.