Interface of Grafted and Ungrafted Silica Nanoparticles with a Polystyrene Matrix: Atomistic Molecular Dynamics Simulations

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• 作者：Tinashe V. M. Ndoro ; Evangelos Voyiatzis ; Azadeh Ghanbari ; Doros N. Theodorou ; Michael C. Bo虉hm ; Florian Mu虉ller-Plathe
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：April 12, 2011
• 年：2011
• 卷：44
• 期：7
• 页码：2316-2327
• 全文大小：1018K
• 年卷期：v.44,no.7(April 12, 2011)
• ISSN：1520-5835

文摘

Atomistic molecular dynamics simulations of a composite consisting of an ungrafted or a grafted spherical silica nanoparticle embedded in a melt of 20-monomer atactic polystyrene chains have been performed. The structural properties of the polymer in the vicinity of a nanoparticle have been studied. The nanoparticle modifies the polymer structure in its neighborhood. These changes increase for higher grafting densities and larger particle diameters. Mass and number density profiles show layering of the polymer chains around the nanoparticle, which extends to 2 nm. In contrast, the increase in the polymer鈥檚 radius of gyration and other induced ordering (alignment of the chains parallel to the surface and orientation of backbone segments) are shorter-ranged. The infiltration of free polystyrene chains into the grafted chains region is reduced with increasing grafting density. Therefore, the interpenetration of grafted and free chains at high grafting densities, which is responsible for the mechanical anchoring of nanoparticles in the polystyrene matrix, is less than what would be desirable for a well-reinforced composite.