Polymer/inorganic particle nanocomposites (or nanodielectrics) have attracted pronounced attention for electric energy storage applications, based on a hypothesis that polymer nanodielectrics could combine the high permittivity of nanoparticles and the high electrical breakdown strength of the polymer matrix for enhanced dielectric performance. Although higher discharged energy densities have been reported for numerous polymer nanodielectrics, the dielectric loss mechanisms, which are extremely important for ultimate applications, are rarely discussed. In this work, we intend to address the intrinsic dielectric loss mechanisms associated with polymer nanodielectrics using a model system comprised of 70 nm BaTiO3 nanoparticles (BT NPs) in an isotactic polypropylene (PP) matrix. The effect of space charge-induced interfacial polarization on dielectric losses was investigated using bipolar and unipolar electric displacement -electric field (D-E) loop tests. Since the bipolar D-E loops always exhibited greater nonlinearity than the unipolar loops, the dielectric loss was attributed to the internal AC conduction loss from space charges (e.g., electrons) in the BT NPs, including boundary layer and bulk conductions. To mitigate the internal conduction along the PP/BT interface, atomic layer deposition of a nanolayer (5 nm) of amorphous TiO2 was applied to the BT NPs. Due to a higher resistivity, the coated amorphous TiO2 effectively reduced the boundary layer conduction loss. Nonetheless, the bulk conduction loss in BT NPs still needed to be reduced. This study suggests that more insulating high permittivity NPs are demanded for polymer nanodielectrics to enhance the dielectric performance.

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We designed and synthesized a novel quaternary ammonium methacrylate compound (QAC-2) bearing a perfluoroalkyl tail on one end and an acrylic moiety on the other. Via one-step UV curing of QAC-2 and methyl methacrylate (MMA) with ethylene glycol dimethacrylate (EGDMA) as the cross-linker, we obtained cross-linked coatings with excellent antimicrobial property, as demonstrated by the total kill against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus epidermidis (S. epidermidis) at a QAC-2 concentration as low as ∼0.06 mol % (∼0.4 wt %) relative to MMA, which was substantially lower than the QAC amount needed in the coatings containing QACs with a hydrocarbon tail. A zone of inhibition test confirmed that the antimicrobial effect was on the basis of contact killing and there was no leaching of antimicrobial species from the cross-linked coating. The high antimicrobial potency in QAC-2-containing films was the consequence of strong surface enrichment of the fluorinated QAC, as confirmed by X-ray photoelectron spectroscopy (XPS).

Mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with controlled molecular weights and narrow polydispersities were synthesized from asymmetric difunctional initiator (Y-initiator)-functionalized 67 nm silica nanoparticles by sequential surface-initiated atom transfer radical polymerization of tBA at 75 °C and nitroxide-mediated radical polymerization of styrene at 120 °C in the presence of a free initiator in each polymerization. The Y-initiator-functionalized nanoparticles were prepared by the immobilization of a triethoxysilane-terminated Yinitiator onto the surface of 67 nm silica particles via an ammoniacatalyzed hydrolysis and condensation process. Transmission electron microscopy studies showed that mixed PtBA/PS brushes grafted on 67 nm silica nanoparticles with comparable molecular weights for the two polymers underwent lateral microphase separation after being cast from CHCl 3 and annealed with CHCl 3 vapor, producing distinct truncated wedge-shaped nanostructures. In contrast, under the same conditions, mixed PtBA/ PS brushes grafted on 160 nm silica particles self-assembled into nanodomains with a more uniform width. This suggests that the truncated wedge-shaped nanostructures formed by mixed brushes on 67 nm silica nanoparticles originated from a higher substrate curvature.