High Interfacial Activity of Polymers 鈥淕rafted through鈥?Functionalized Iron Oxide Nanoparticle Clusters

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• 作者：Lynn M. Foster ; Andrew J. Worthen ; Edward L. Foster ; Jiannan Dong ; Clarissa M. Roach ; Athena E. Metaxas ; Clifford D. Hardy ; Eric S. Larsen ; Jonathan A. Bollinger ; Thomas M. Truskett ; Christopher W. Bielawski ; Keith P. Johnston
• 刊名：Langmuir
• 出版年：2014
• 出版时间：September 2, 2014
• 年：2014
• 卷：30
• 期：34
• 页码：10188-10196
• 全文大小：340K
• ISSN：1520-5827

文摘

The mechanism by which polymers, when grafted to inorganic nanoparticles, lower the interfacial tension at the oil鈥搘ater interface is not well understood, despite the great interest in particle stabilized emulsions and foams. A simple and highly versatile free radical 鈥済rafting through鈥?technique was used to bond high organic fractions (by weight) of poly(oligo(ethylene oxide) monomethyl ether methacrylate) onto iron oxide clusters, without the need for catalysts. In the resulting 鈭? 渭m hybrid particles, the inorganic cores and grafting architecture contribute to the high local concentration of grafted polymer chains to the dodecane/water interface to produce low interfacial tensions of only 0.003 w/v % (polymer and particle core). This 鈥渃ritical particle concentration鈥?(CPC) for these hybrid inorganic/polymer amphiphilic particles to lower the interfacial tension by 36 mN/m was over 30-fold lower than the critical micelle concentration of the free polymer (without inorganic cores) to produce nearly the same interfacial tension. The low CPC is favored by the high adsorption energy (鈭?0⁶ k_BT) for the large 鈭? 渭m hybrid particles, the high local polymer concentration on the particles surfaces, and the ability of the deformable hybrid nanocluster cores as well as the polymer chains to conform to the interface. The nanocluster cores also increased the entanglement of the polymer chains in bulk DI water or synthetic seawater, producing a viscosity up to 35鈥?00 cP at 0.01 s^鈥?, in contrast with only 600 cP for the free polymer. As a consequence of these interfacial and rheological properties, the hybrid particles stabilized oil-in-water emulsions at concentrations as low as 0.01 w/v %, with average drop sizes down to 30 渭m. In contrast, the bulk viscosity was low for the free polymer, and it did not stabilize the emulsions. The ability to influence the interfacial activity and rheology of polymers upon grafting them to inorganic particles, including clusters, may be expected to be broadly applicable to stabilization of emulsions and foams.