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    Anthony Was

    Nanoscale control over the structures is critical in designing nanocomposites with advanced properties. Structural parameters such as interface and volume fraction of reinforcement have tremendous effects on the mechanical properties of... more
    Nanoscale control over the structures is critical in designing nanocomposites with advanced properties. Structural parameters such as interface and volume fraction of reinforcement have tremendous effects on the mechanical properties of the nanocomposites, yet have proven difficult to control uniformly and consistently. Here we investigate the effect of reinforcement and interface on the finite deformation response of polyurethane (PU-) montmorillonite
    ... Paul Podsiadlo‡ # , Ming Qin‡, Charles M. Shaw ¶ , Anthony M. Waas, Nicholas A. Kotov‡ and Ellen M. Arruda* ¶. † Department of Mechanical Engineering. ‡ Department of Chemical Engineering. § Department of Aerospace Engineering.... more
    ... Paul Podsiadlo‡ # , Ming Qin‡, Charles M. Shaw ¶ , Anthony M. Waas, Nicholas A. Kotov‡ and Ellen M. Arruda* ¶. † Department of Mechanical Engineering. ‡ Department of Chemical Engineering. § Department of Aerospace Engineering. Department of Biomedical Engineering ...
    This paper discusses the role of the structural disjoining pressure exerted by nanoparticles on the spreading of a liquid film containing these particles. The origin of the structural disjoining pressure in a confined geometry is due to... more
    This paper discusses the role of the structural disjoining pressure exerted by nanoparticles on the spreading of a liquid film containing these particles. The origin of the structural disjoining pressure in a confined geometry is due to the layering of the particles normal to the confining plane and has already been traced to the net increase in the entropy of the system in previous studies. In a recent paper, Wasan and Nikolov (Nature, 423 (2003) 156) pointed out that the structural component of the disjoining pressure is strong enough to move a liquid wedge; this casts a new light on many applications—most notably, detergency. While the concept of spreading driven by the disjoining pressure is not new, the importance of the structural disjoining pressure arises from its long-range nature (as compared to the van der Waals' force), making it an important component of the overall force balance near the contact line. In this paper, we report on a parametric study of the spreading phenomena by examining the effects of nanoparticle size, concentration and polydispersity on the displacement of an oil–aqueous interface with the aqueous bulk containing nanoparticles. The solution of the extended Laplace–Young equations for the profile of the meniscus yields the position of the nominal contact line under the action of the structural disjoining pressure. Simulations show that the displacement of the contact line is greater with a high nanoparticle volume fraction, small particles for the same volume fraction, monodispersed (in size) particles rather than polydispersed particles and when the resisting capillary pressure is small, i.e., when the interfacial tension is low and/or the radius of the dispersed phase drop/bubble is large.