Temperature-Induced Transport of Thermosensitive Hairy Hybrid Nanoparticles between Aqueous and Organic Phases

• Published in: Langmuir Vol. 23; no. 4; pp. 2208 - 2217
• Main Authors: Li, Dejin, Zhao, Bin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.02.2007
• Subjects: Chemistry; Colloidal state and disperse state; Electrochemistry; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Water; Nanoparticle; Alcohol; Silica; Interfacial area; Ethylene oxide polymer; Particle; Transport process; Cloud point; Alkanol; Hydrocarbon; Toluene; Stirring; Polymerization; Polymer; Ice; Acetate; Droplet; Liquid; Heating; Phase separation; Electrochemistry; Benzenic compound; Butanol; Transport
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0628165

This paper reports on the temperature-induced transport of thermosensitive polymer brush-grafted silica nanoparticles between aqueous and organic phases. Poly(methoxytri(ethylene glycol) methacrylate), a thermosensitive water-soluble polymer with a cloud point of ∼48 °C in H2O, was grown on silica nanoparticles by surface-initiated atom transfer radical polymerization in the presence of a free initiator. These hairy particles were found to quantitatively transfer from aqueous to ethyl acetate phases upon heating at 60 °C under the stirring condition. Cooling in an ice/water bath caused the particles to move from ethyl acetate to the aqueous layer. The concentrations of the particles in the original phases during the transport processes were monitored by UV−vis spectrometry. When mutually saturated water and ethyl acetate were used, the transport rates of the particles between the two phases were enhanced. The faster transport was attributed to the solvent phase separation, which produced liquid droplets, dramatically increased the interfacial area, and hence facilitated the transport of the particles. The reversible transfer of the particles between the aqueous and ethyl acetate phases upon heating at 60 °C and cooling in an ice/water bath can be repeated consecutively at least 10 times. The hairy particles can also be quantitatively transported from 1-butanol and toluene to H2O by stirring in an ice/water bath. However, only 60% of the particles transferred from water to 1-butanol and no particles to toluene upon heating at 60 °C. The reasons are discussed.