Organizing Anisotropic Nanoparticles in Block Copolymer Nanocomposites

Orateur : Russell J. COMPOSTO (Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA)

Polymer nanocomposites (PNCs) are formed by incorporating nanoparticles (NPs) into polymeric matrices. PNC properties depend not only on the character istics of each component, but also on the distribution, organization, and, for anisotropic NPs, the orientation of the inclusions [1-2]. However, the precise alignment of anisotropic NPs in PNCs via self-assembly has received limited attention. The first study investigates nanorod alignment in poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) films with vertical P2VP cylindrical domains [3]. Gold nanorods (NRs) locate parallel to the near-surface region either bridging domains or within a domain depending on length. A minority of NRs orient vertically. Free energy calculations using self-consistent field theory are used to interpret the experimental results. The second study investigates lamellar-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) films with domains parallel to the substrate as a platform to align nanoplates of gadolinium trifluoride (GdF3:Yb/Er). The GdF3:Yb/Er not only segregate to the PMMA domain, but also show alignment in the lamellae up 20 wt%. Beyond 20 wt%, the block copolymer is disordered and the nanoplates are randomly oriented. These results extend our understanding of PNC phase behavior, enabling us to design and create new, self-assembling anisotropic materials with unique plasmonic (AuNR) and upconverting (GdF3:Yb/Er) properties.

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