Use of different size grids to control the surface chemistry of plasma‐polymerized acrylic acid films in a hybrid discharge

The surface chemistry of plasma‐polymerized acrylic acid (ppAc) films were controlled in a two‐stage (primary and processing) hybrid radio frequency (RF) discharge by changing the grid wire spacing (d_s). Two regions were defined in terms of d_s with respect to Debye length (λ_d) in the primary chamber at the grid to control the electron temperature (T_e) and surface chemistry of the ppAc films deposited in the processing chamber. A higher T_e (>3 eV) in the processing plasma was possible for d_s > λ_d, whereas decreasing d_s relative to λ_d reduced T_e. X‐ray photoelectron spectroscopy was used to characterize the ppAc films deposited on a glass substrate. The ppAc films surface characterization showed the maximum proportion of carbon atoms as carboxylic/ester [C(?O)OX] functionalities in C1s at the surface of films for the grid with d_s ≈ λ_d. The proportion of carbon atoms as ? [C(?O)OX] and COX in C1s at the surface decreased when d_s decreased relative to λ_d. The proportion of carbon atoms as carbonyl (C?O) at the film surface showed very good stability for all of the d_s values explored in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2219–2224, 2007