My research focus is developing high-performance hybrid nanocomposites that contain polymer chains in molecular scale confinement. In composite materials, the strategy of intermixing the organic, soft phase with a hard phase is used to achieve desirable properties. As a result, the soft phase is spatially confined and constrained by the hard phase. Molecular scale confinement of polymers occurs in hybrid nanocomposites prepared by filling nanoporous hybrid glass with polymers. Such molecular scale confinement of polymers have intrigued increasing research interest recently not only due to polymer physics topics like enhanced polymer mobility and local polymer dynamics, but also because the fracture and mechanical properties of the nanocomposites could be greatly improved by the confinement. We have shown that in such nanocomposites, the confined polymers dissipate energy through a confinement-induced molecular bridging mechanism. Hybrid nanocomposites could be potentially used in a lot of applications including high strength thin films, protective coatings and adhesion promoting films.
One of my research interest is that how surface modification of the porous glass matrix would affect the mechanical properties of the hybrid nanocomposites. The nanoporous hybrid glass I have been using is an organosilicate synthesized by sol-gel chemistry. The nature of the pore surface of the glass matrix can be dramatically altered by surface functionalization in which chemical groups are anchored on the pore surface, and the surface functionalization can be characterized by a variety of techniques including contact angle measurement of the matrix surface (Figure 1). It turns out that pore surface functionalization of the matrix significantly influences the toughness of the resulting hybrid nanocomposite, because the strength of the interaction between the matrix and the polymer is tuned by such functionalization.
While the surface chemistry of the glass matrix can be modified to make an impact on the mechanical properties of the nanocomposite, we can also choose the polymer filler from a wide range of polymers. We have observed that the choice of the polymer filler is also critical to the mechanical properties of the nanocomposite.
So a question we want to ask is, what is the best combination of surface chemistry and polymer filler to maximize the mechanical properties? My future studies will attempt to answer that by understanding in details how the interaction between polymers and the modified pore surface would affect the mechanical properties of the nanocomposite.
Figure 1: Scheme of pore surface modification and water contact angle of different types of modified matrix.
C. Wang, S. G. Isaacson, K. Lionti, W. Volksen, T. P. Magbitang, G. Dubois, R. H. Dauskardt. Toughening Hybrid Nanocomposites with Molecularly Confined Polymers by Chemically Tuning the Polymer-Surface Interaction. ACS 253rd National Meeting & Exposition 2017, San Francisco, CA.