Exploring lateral microphase separation in mixed polymer brushes by experiment and self-consistent field theory simulations

Similar to block copolymers, mixed polymer brushes are physically constrained and, upon annealing, microphase separate into nanodomains with morphologies largely dependent on the volume fractions of the polymers. A combination of experimental analysis of polystyrene (PS)/poly(methyl methacrylate) (PMMA) brushes and self-consistent field theory (SCFT) simulations is employed to determine the phases of annealed binary brushes. By annealing the brushes under conditions that maximize lateral versus vertical separation, a rich array of phases are observed with general agreement to predictions by SCFT simulations. The incorporation of random perturbations to the grafting density in SCFT simulations accounts for disorder in the arrangement of the polymer domains for the PS/PMMA brushes. Additionally, autocorrelation of the polymer domains yields an experimental domain spacing that is nearly 2 times greater than SCFT predictions, which is hypothesized to result from polydispersity in the PS/PMMA brushes. These findings should provide a basis for the improved fabrication of nanopatterned mixed polymer brushes with implications for the enhancement of biological surfaces, membranes, and nanolithography. © 2011 American Chemical Society.