Order and Phase Behavior of a Cylinder Forming Diblock Copolymers and Nano-Particles Mixture in Confinement: A Molecular Dynamics Study Lenin S. Shagolsem,* Jens-Uwe Sommer Introduction For the past few decades, mixtures of polymers and nano- particles have been a subject of intense research. For example, mixtures of diblock-copolymers (DBCs) and nano- particles (NPs) are shown to have improved the quality of polymer materials by producing highly ordered and complex composite structures which can serve as a next generation catalysts, selective membranes, and photonic band gap materials. [1–3] Block-copolymer nano-templates are also used in producing ordered arrays of metal dots or nanowires. [4] In addition to the well known ordered phases of a pure DBC melt, DBC-NP mixtures show new self- assembled morphologies. [5] A pure DBC melt can be completely characterized by the product xN and block Full Paper L. S. Shagolsem Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany E-mail: shagolsem@ipfdd.de J.-U. Sommer Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany and Institute of Theoretical Physics, Technische Universita ¨t Dresden, 01069 Dresden, Germany We study a coarse grained model of cylinder forming diblock copolymers and nano-particles (NPs) mixture confined between Lennard–Jones hard walls. Two models for non-selective interactions between monomers and NPs are applied. In the case of purely repulsive inter- actions between NPs and monomers (athermal case) strong segregation of NPs at the film sur- faces and the formation of droplets of particles inside the copolymer film can be observed. For weakly attractive interactions between NPs and monomers (thermal case) formation of droplets of particles disappears and segregation on the film surfaces depend on temperature. The uptake of NPs by the copolymer film in the thermal case displays a non-monotonic dependence on temperature which can be qualitatively explained by a mean-field model. In both cases of non- selective interactions NPs are preferentially loca- lized at the interface between the microphase domains. Macromol. Theory Simul. 2011, 20, 329–339 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com DOI: 10.1002/mats.201000095 329