Synthesis and Fabrication of Multifunctional Nanocomposites: Stable Dispersions of Nanoparticles Tethered with Short, Dense and Polydisperse Polymer Brushes in Poly(methyl methacrylate)
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This paper presents a melt-processable multifunctional nanocomposite material that shows highly controlled tunability in refractive index, glass transition temperature (T g) and energy bandgap. ZnO quantum dots tethered with polymer brushes are melt-blended into the matrix polymer, giving rise to multiple functionalities in the nanocomposites. Brush-matrix polymer interactions are important in determining the ability of polymer-grafted nanoparticles to disperse in a polymer melt, of which graft density (), brush (N) and matrix (P) polymer lengths are the critical parameters. It is generally assumed that long polymer brushes (N > P) and an optimum graft density are necessary to achieve a good dispersion. Here it is demonstrated that nanoparticles tethered with short, dense and polydisperse polymer brushes via radical copolymerization can exhibit a stable, fine dispersion in the polymer melt. The quality of the dispersion of the nanoparticles is characterized by measuring physical properties that are sensitive to the state of the dispersion. This synthesis method presents a general approach for the inexpensive and high-throughput fabrication of high quality, melt-blendable nanocomposites that incorporate functional nanoparticles, paving the way for wider application of high performance nanocomposites. Nanoparticles tethered with short, dense and polydisperse polymer brushes exhibit excellent compatibility and stability in a poly(methyl methacrylate) matrix, despite the large mismatch in molecular weights of matrix polymer and grafted polymer. Polymer brushes are prepared through free radical polymerization, which is generally applicable to a wide range of nanoparticle-nanocomposite combinations. The tunability of multifunctional properties of these hybrid materials is reported. Copyright 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.