Abstract
Based on the Pickering emulsion template method, two types of Janus particles with different relative amphiphilic areas for stabilizing non-aqueous foam were synthesized. In addition, particles with uniformly modified surface were synthesized for comparison. By adjusting oil mixtures, the behavior of particles on the oil-air surface was measured. Moreover, the role of particle agglomerates in surface adsorption process was investigated. Affected by the particle surface contact angle, the surface activity of Janus particles is not always greater than that of uniformly modified particles, which is reflected on delta surface tension and the volume of foam generated. The oil-surface adsorption process of synthesized Janus particles is not only occurred in the form of independent detached particles, but also in the form of particle agglomerates. The adsorption of the particles from the bulk phase to the surface requires the contact angle of the Cassie–Baxter composite surface of the particle agglomerates to be around 90°, but the inherent contact angle of the individual particles is <90°.
Highlights
In the past two decades, foams stabilized by colloidal particles have attracted the interest of many researchers (Murray and Ettelaie, 2004; Sun et al, 2015; Asghari et al, 2016; Narsimhan, 2016; Wang and Nguyen, 2016; Sakthivel et al, 2019)
The oil-air surface properties were adjusted by changing the ratio of each substance in the oil mixture, and the behavior of the particles on various oil-air surfaces was measured. In this process we found that particle agglomerates play a significant role in particle adsorption to the surface
Hydrophilic silica particles were purchased from NPS Chemical Company (d50 = 195 nm, specific surface area 14 m2/g). 3-aminopropyltriethoxysilane(APS), N-octyltriethoxysilane (OTS), 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFTS), perfluorooctanoic acid (PFOA), fluorescein5(6)-isothiocyanate (FITC), n-octanoic acid (OA), and triethylamine were purchased from Aldrich
Summary
In the past two decades, foams stabilized by colloidal particles have attracted the interest of many researchers (Murray and Ettelaie, 2004; Sun et al, 2015; Asghari et al, 2016; Narsimhan, 2016; Wang and Nguyen, 2016; Sakthivel et al, 2019). The high surface tension caused by hydrogen bonds at the water-air surface makes the aqueous surface extremely susceptible to adsorption of surface-active components, and such aqueous systems are prone to foaming Other fluids, such as hydrocarbons, have significantly lower surface tension. Compared with the homogeneous particles, amphiphilic Janus particles (De Gennes, 1992) can increase the surface activity up to 3 times (Binks and Fletcher, 2001; Glaser et al, 2006) Such particles, which are more adsorbed toward the interface, can provide better long-term stability of emulsions and foams. In this process we found that particle agglomerates play a significant role in particle adsorption to the surface
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