Effect of van der Waals Interaction Strength and Nanocluster Size on the Dynamical and Mechanical Properties of 1,4-cis-
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Effect of van der Waals Interaction Strength and Nanocluster Size on the Dynamical and Mechanical Properties of 1,4-cis-polybutadiene Melts Canan Atilgan, Ibrahim Inanc and Ali Rana Atilgan Faculty of Engineering and Natural Science, Sabanci University, Istanbul, Turkey ABSTRACT Using molecular dynamics simulations, we have investigated the effect of embedding nanoclusters of radius 3-7 Å on the dynamical and mechanical properties of 1,4-cispolybutadiene melts. To see the effect of polymer-nanocluster interaction strength on the bulk modulus, the van der Waals interactions (vdW) between the polymer chain and nanocluster have been varied from weak to very stong while keeping polymer-polymer and nanoclusternanocluster interactions constant. The modulus depends on the interaction strength, but not on nanocluster size. Residence time of chains on the surface of the nanocluster (τr) has an increasing trend that reaches to a plateau as the vdW strength is increased. τr also doubles from 100 ps to 200 ps as the nanocluster size is increased from 3 to 7 Å. Our findings give clues on how the properties of polymeric materials may be controlled by nanoparticles of different chemistry and size. INTRODUCTION Polymer matrix based nanocomposites have been attracting research interest due to their promise to improve materials mechanical properties such as higher stiffness, impact and tensile strength, rheological, viscoelestic and physical properties [1-4]. Since it is a big challenge to characterize the structure and properties and manipulate the fabrication process, until now development of nanocomposites have mostly been empirical [5]. In the last decade, computer modeling and simulations have been holding an increasing role in understanding and controlling the underlying mechanism of such property changes and enhancements [6, 7]. Fundamental issues such as molecular origin of reinforcement, rheological behavior for better processing and structure and dynamics at the interface of the matrix and the filler are the main purpose of these modeling and simulation efforts. Different computational methods, ranging from molecular to macro scale, such as molecular dynamics (MD) [8-10], Monte Carlo [11, 12], dissipative particle dynamics [13], lattice Boltzmann [14], equalivant-continuum [15] and finite element methods [16], have been used for this purpose. In nanocomposites, interplay of different parameters such as temperature, filler size and shape, mixing ratio of matrix and filler, polymer type and size play significant roles in the enhanced materials properties [17]. Yet, few computational approaches have addressed the affect of those parameters systematically. In this manuscript, results of a systematic study of a model polymer matrix reinforced by a nanoparticle are presented. The nanoparticle is modeled at the atomistic detail which allows us to determine the dynamical and mechanical properties. A nanoparticle that interacts via vdW with the chains are incorporated and the effect of interaction strength is varied. Furthermore, th
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