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Beyond Patterns to Mechanisms. Multiscale Molecular Simulations of Nanoparticles/block Copolymers Self-Assembled Bulk Nanocomposites

Sabrina Pricl1, Paola Posocco1, Marek Mály2, Martin Lisal2, and Maurizio Fermeglia1. (1) Molecular Simulation Engineering (MOSE) Laboratory - DICAMP, University of Trieste, Piazzale Europa 1, Trieste, 34127, Italy, (2) E. Hala Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, 6-Suchdol, Prague, 165 02, Czech Republic

Self-assembly is emerging as an elegant, bottom-up method for fabricating nanostructured materials. This approach becomes particularly powerful when the ease and control offered by the self-assembly of organic components is combined with the electronic, magnetic or photonic properties of inorganic components. To achieve a high level of control of the dispersion state of the inorganic particles and the morphology of the polymer matrix in these composite materials, however, new synthetic routes must be developed to manipulate both the inorganic fillers and the polymers at the nanoscale. Recently, it has been suggested that block copolymers, with their vast variety of morphologies arising from their microphase separation property, can constitute effective means to control particle location and dispersion. These techniques, based on the self-assembly of nanoparticles into one micro-domain of the block copolymers, is versatile to prepared nanocomposite systems with different matrix morphologies and embedded particles organized in a plethora of possible patterns. Such spatially regular nanocomposite materials will clearly have high impact in nanotechnology, in that their peculiar magnetic, optic, electrical, and mechanical properties could be exploited for novel, advanced applications. As examples, materials with enhanced 2D or 3D ordering of nanoparticles in ordered polymer-based matrices can be best candidates for advanced catalysis applications, as selective membranes, and as magnetic and photonic band gap materials.

A few approaches have been proposed for the incorporation of nanoparticles into the preferred domain of block copolymers in a selective, well-ordered fashion. Since the ultimate properties of the final nanostructured material will strongly depend upon the degree of dispersion and ordering of the particles in the polymer matrix, tailoring nanoparticles into arrays in a geometrically well-defined macromolecular phase will provide endless and exciting new possibilities on the materials front. Thus, a detailed understanding of the effects of the molecular properties of block copolymers and nanoparticles on the self-assembled structures of the corresponding nanocomposites is essential to develop strategies to fabricate new composites with unique structural and functional properties.

To gain a better insight into the thermodynamic aspects of organizing nanoparticles in ordered microphase-separated domains, in this work we focused on the distribution of nanoparticles of different coverage, shape and volume fraction in diverse morphologies of a diblock copolymer by large-scale three-dimensional dissipative particle dynamics (DPD) simulations. As a further aspect of novelty, in the framework of the DPD interaction parameters were derived from lower scale simulations, i.e., atomistic molecular dynamics, according to an original mapping procedure and in the framework of our well-known multiscale computational approach. In order to compare our results with experimental information, we considered a composite system made up by poly(styrene-b-2vinylpiridine) (PS-PVP) and gold nanoparticles.