We investigate the phase behavior of symmetric AB diblock copolymers confined into a thin film. The film boundaries are parallel, impenetrable and attract the A component of the diblock copolymer. Using a self-consistent field technique [M.W. Matsen, J.Chem. Phys. 106, 7781 (1997)], we study the ordered phases as a function of incompatibility χ and film thickness in the framework of the Gaussian chain model. For large film thickness and small incompatibility, we find first order transitions between phases with different number of lamellae which are parallel oriented to the film boundaries. At high incompatibility or small film thickness, transitions between parallel oriented and perpendicular oriented lamellae occur. We compare the self-consistent field calculations to Monte Carlo simulations of the bond fluctuation model for chain length N = 32. In the simulations we quench several systems from χN = 0 to χN = 30 and monitor the morphology into which the diblock copolymers assemble. Three film thicknesses are investigated, corresponding to parallel oriented lamellae with 2 and 4 interfaces and a perpendicular oriented morphology. Good agreement between self-consistent field calculations and Monte Carlo simulations is found. I. INTRODUCTION.Amphiphilic polymers are model systems for investigating mechanisms of self-assembly. Joining chemically distinct polymers -A and B -at their ends to form an AB diblock copolymer prevents macrophase separation of the two species. In order to reduce the number of energetically unfavorable interactions between distinct blocks in a melt, the molecules self-assemble into complex morphologies. The morphology is selected via a delicate balance between the free energy cost of the internal interfaces and the conformational entropy loss as the molecules stretch to fill space at constant density. The phase diagram in the bulk has been investigated in much detail as a function of the relative length of the blocks f and the incompatibility χN [1-3]. The morphologies found in copolymer melts and copolymer/homopolymer mixtures [4] resemble the spatially structured phases of other amphiphilic systems (e.g., lipid/water mixtures).From a theoretical point of view, polymeric systems are particularly convenient for investigating mechanisms of self-assembly. Only a small number of parameters describe the system, i.e., the fraction f of A monomers in the diblock, the molecule's end-to-end distance R e and the incompatibility χN , where χ denotes the repulsion between monomers of different species and N the number of monomers per molecule. In general, polymeric systems are well describable by self-consistent field theories using the Gaussian chain model [5][6][7]. For a wide range of temperature the theory accurately calculates the excess quantities of the internal interfaces (e.g., the interfacial tension, the bending moduli, or the enrichment of solvent). The understanding of these interfacial properties makes polymers suitable microscopic model systems for investigating the statistical mechanics ...

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We investigate interfacial properties between two highly incompatible polymers of different stiffness. The extensive Monte Carlo simulations of the binary polymer melt yield detailed interfacial profiles and the interfacial tension via an analysis of capillary fluctuations. We extract an effective Flory-Huggins parameter from the simulations, which is used in self-consistent field calculations. These take due account of the chain architecture via a partial enumeration of the single chain partition function, using chain conformations obtained by Monte Carlo simulations of the pure phases. The agreement between the simulations and self-consistent field calculations is almost quantitative, however we find deviations from the predictions of the Gaussian chain model for high incompatibilities or large stiffness. The interfacial width at very high incompatibilities is smaller than the prediction of the Gaussian chain model, and decreases upon increasing the statistical segment length of the semi-flexible component. IntroductionMelt blending of polymers has proven useful in designing new composite materials with improved application properties. In many practical situations the constituents of the blend are characterized by some degree of structural asymmetry. For example, a flexible component might contribute to a higher resistance to 1 fracture, while blending it with a stiffer polymer can increase the tensile strength of the material. Since the entropy of mixing in polymeric systems decreases with increasing degree of polymerization, a small unfavorable mismatch in enthalpic interactions, entropic packing effects or the combination of both, generally leads to materials which are not homogeneous on mesoscopic scales, but rather fine dispersions of one component in another. Therefore properties of interfaces between unmixed phases are crucial in controlling the application properties of composites [1] and have found abiding experimental interest [2,3,4,5]. Recently, the bulk phase behavior and surface properties [6] of polyolefins [7,8] with varying microstructure has attracted considerable experimental and theoretical interest. These mixtures are often modeled [7,9,10] as blends of polymers with different bending rigidities, the less branched polymer corresponding to the more flexible component. For pure hard core interactions, field theoretical calculations by Fredrickson, Liu and Bates[9], polymer reference interaction site model (P-RISM) computations by Singh and Schweizer[10], lattice cluster theories by Freed and Dudowicz [11] and Monte Carlo simulations [12] find a small positive contribution to the Flory-Huggins parameter χ. Monte Carlo simulations which include a repulsion between unlike species reveal an additional increase of the effective Flory-Huggins parameter with chain stiffness, because a back folding of chains becomes less probable with increasing stiffness and the number of intermolecular contacts increases [12] respectively. Qualitatively similar effects were found analytically in P-RISM[10]...