Symmetric diblock copolymer thin films confined between homogeneous and patterned surfaces: Simulations and theory

Wang, Qiang; Nath, Shyamal K.; Graham, Michael D.; Nealey, Paul F.; de Pablo, Juan J.

doi:doi:10.1063/1.481635

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Theoretical investigation of water formation on Rh and Pt Surfaces

Catalytic water formation from adsorbed H and O adatoms is a fundamental reaction step in a variety of technologically important reactions involving organic molecules. In particular, the water-formation rate determines the selectivity of the catalytic partial oxidation of methane to syngas. In this report we present a theoretical investigation of the potential-energy diagram for water formation from adsorbed O and H species on Rh(111) and Pt(111) surfaces. The study is based on accurate first-pr...

Interfacial profiles of mismatched lamellae in thin diblock copolymer films

A number of recent experiments have allowed direct study of diblock copolymer morphology on patterned surfaces. Here we examine, by computer simulation, the morphology of a diblock thin film in contact with a substrate having large stripes. The diblock aligns parallel to the surface but is frustrated at the point where two stripes join. We show here that at the joint one of the phases is continuous while the other is discontinuous. In the region of the join the lamellae form a kink with a length...

We have investigated the ability of a simple phenomenological theory to describe the behavior of symmetric diblock copolymer thin films confined between two hard surfaces. Prior knowledge of the morphology in the confined films is crucial for applying this theory to predict the phase diagram of such systems. Taking advantage of our observations in Monte Carlo simulations, we use the theory to construct phase diagrams for thin films confined between patterned-homogeneous surfaces, and obtain good agreement with our results of simulations. Two conditions are essential for obtaining long-range ordered perpendicular lamellae: a lower stripe-patterned surface with the surface pattern period L_s comparable to the bulk lamellar period L₀, and an upper neutral or weakly preferential surface. We have also examined the undulation of perpendicular lamellae between two hard surfaces. For the cases of two homogeneous (preferential) surfaces and patterned-preferential surfaces, our calculations using the phenomenological theory indicate that the amplitudes of the undulation are on the same order of magnitude as observed in our Monte Carlo simulations, and are one order of magnitude larger than previously reported. The theory, however, is unable to capture the shape of the undulation. For the case of patterned-neutral surfaces, we find that an earlier analysis is unable to yield the undulations that would stabilize the perpendicular lamellar morphology. We have addressed this issue and obtained undulations that are consistent with our observations from Monte Carlo simulations. © 2000 American Institute of Physics.