Adsorption of random copolymers from a melt onto a solid surface: Monte Carlo Studies

Authors:

• Jarosław Sylwester Kłos,
• Dirk Romeis,
• Jens Uwe Sommer

Abstract

We study the behavior of random AB-copolymer melts near a selective surface. We consider the case where the copolymers do not display phase segregation behavior in the bulk but the surface is strongly selective for the A-component and the probability of finding an A-monomer along the chain is p⪡1. Using self-consistent field theory and scaling arguments, we discuss some aspects of conformational rearrangements and composition selection in the surface layer. For strong selectivity we discuss the formation of a polydisperse brush on the surface. Next, we consider selection mechanisms of chains and sequences of A-species in the surface layer. We used the bond-fluctuation method to simulate copolymer melts at different values of the surface selectivity. Several aspects of the surface layer are analyzed, such as the composition profiles, chemical composition of chains on the surface, chain extension, and dynamics. We find evidence for conformational rearrangements in the surface layer according to the polydisperse brush model, as well as enrichment of A-monomers in the adosorbed chains, stretching of chains in the direction perpendicular to the surface, and selection of multiple A-sequences. Slight but systematic variation of the properties of surface layer at long simulation times indicates that selection processes require very long time scales as expected from theoretical arguments.