Engineering

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Browsing Engineering by Author "Huang, Lingqi"

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    Efficient, robust surface functionalization and stabilization of gold nanorods with quaternary ammonium-containing ionomers as multidentate macromolecular ligands
    (2016-04-25) Dong, Zhongmin; Xiang, Peng; Huang, Lingqi; Ye, Zhibin
    Surface functionalization of gold nanorods (GNRs) is critical to their applications in various fields. While there are several existing strategies, we report in this article a new general strategy for the surface functionalization of GNRs with quaternary ammonium-containing ionomers as a novel class of multidentate macromolecular surface ligands. A range of tetralkylammoniumcontaining hyperbranched polyethylene- and linear poly(n-butyl acrylate)-based ionomers has been specifically designed and employed in the strategy. Acting as multidentate macromolecular analogues of cetyltrimethylammonium bromide (CTAB), the ionomers have been demonstrated to bind onto the GNR surface by displacing the surface-bound CTAB species via ligand exchange to render CTAB-free ionomer-modified GNRs. By properly designing the enabling ionomers, we have shown that the modified GNRs can be endowed with some desired properties, such as excellent dispersibility in various organic solvents, robust stability under multiple rounds (up to 12 investigated) of high-speed centrifugation in organic solvents, amphiphilicity with dispersibility in both aqueous and organic media, fluorescence, and capability in carrying hydrophobic guest species. This strategy thus provides potential new ways for the construction of novel multifunctional GNR nanocomposites.
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    Modification of cellulose nanocrystals with quaternary ammonium-containing hyperbranched polyethylene ionomers by ionic assembly
    (American Chemical Society, 2016-07-25) Huang, Lingqi; Ye, Zhibin; Berry, Richard
    In this article, we demonstrate the first surface modification of cellulose nanocrystals (CNCs) with quaternary ammonium-containing ionomers by ionic binding of their positively charged ammonium ions onto the negatively charged surface of CNCs. A range of hyperbranched polyethylene ionomers (I1–I6) having different ionic content (0.2–2.3 mol %) has been designed and employed for this purpose. The simple dropwise addition and mixing of the aqueous dispersion of CNCs with the ionomer solution in tetrahydrofuran (THF) conveniently renders the ionomer-modified CNCs (mCNC1–mCNC6). The presence of adsorbed ionomers on the modified CNCs is confirmed with spectroscopic and X-ray diffraction evidence and quantified through thermogravimetric analysis. The effects of the ionomer to CNC feed mass ratio and the ionomers of different ionic content on the modification have been examined. A study on the morphology of the modified CNCs by atomic force microscopy discloses the occurrence of side-to-side and/or end-to-end assembly of the CNC rods due to the “cross-linking” or bridging effects of the multidentate ionomers. Because of the hydrophobic hyperbranched polyethylene segments in the adsorbed ionomers, the modified CNCs can be dispersed in nonpolar or low-polarity organic solvents (such as THF, toluene, and chloroform). In particular, the THF dispersions of modified CNCs prepared with ionomers having ionic content ≥0.7 mol % (I3–I6) behave as thixotropic organo-gels at concentrations ≥40 mg mL–1. Further, the modified CNCs better disperse than unmodified CNCs in a hydrophobic ethylene–olefin copolymer (EOC) elastomer matrix and show better thermal stability than a surfactant-modified CNC sample. Tensile testing confirms that the EOC composites, filled with the ionomer-modified CNCs, are significantly reinforced with a tensile modulus nearly doubled that of neat EOC, and they demonstrate better elongation at break relative to those filled with unmodified CNCs or surfactant-modified CNCs.
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    Polycyclopentene crystal-decorated carbon nanotubes by convenient large-scale in situ polymerization and their lotus leaf-like superhydrophobic films.
    (2016-12-22) Ye, Zhibin; Xu, Lixin; Huang, Lingqi; Meng, Nan; Shu, Yang; Gu, Zhiyong
    In situ Pd-catalyzed cyclopentene polymerization in the presence of multi-walled carbon nanotubes (MWCNTs) is demonstrated to effectively render, on a large scale, polycyclopentene-crystal-decorated MWCNTs. Controlling the catalyst loading and/or time in the polymerization offers a convenient tuning of the polymer content and the morphology of the decorated MWCNTs. Appealingly, films made of the decorated carbon nanotubes through simple vacuum filtration show the characteristic lotus-leaf-like superhydrophobicity with high water contact angle (>150°), low contact angle hysteresis (<10°), and low water adhesion, while being electrically conductive. This is the first demonstration of the direct fabrication of lotus-leaf-like superhydrophobic films with solution-grown polymer-crystal-decorated carbon nanotube.