title: Responsive Aqueous Foams Stabilized by Silica Nanoparticles Hydrophobized in Situ with a Conventional Surfactant.
abstract: In the recent past, switchable surfactants and switchable/stimulus-responsive surface-active particles have been of great interest. Both can be transformed between surface-active and surface-inactive states via several triggers, making them recoverable and reusable afterward. However, the synthesis of these materials is complicated. In this paper we report a facile protocol to obtain responsive surface-active nanoparticles and their use in preparing responsive particle-stabilized foams. Hydrophilic silica nanoparticles are initially hydrophobized in situ with a trace amount of a conventional cationic surfactant in water, rendering them surface-active such that they stabilize aqueous foams. The latter can then be destabilized by adding equal moles of an anionic surfactant, and restabilized by adding another trace amount of the cationic surfactant followed by shaking. The stabilization-destabilization of the foams can be cycled many times at room temperature. The trigger is the stronger electrostatic interaction between the oppositely charged surfactants than that between the cationic surfactant and the negatively charged particles. The added anionic surfactant tends to form ion pairs with the cationic surfactant, leading to desorption of the latter from particle surfaces and dehydrophobization of the particles. Upon addition of another trace amount of cationic surfactant, the particles are rehydrophobized in situ and can then stabilize foams again. This principle makes it possible to obtain responsive surface-active particles using commercially available inorganic nanoparticles and conventional surfactants.
authors.affiliation: The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University , 1800 Lihu Road, Wuxi, Jiangsu 214122, People's Republic of China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University , 1800 Lihu Road, Wuxi, Jiangsu 214122, People's Republic of China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Pei
authors.affiliation: The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University , 1800 Lihu Road, Wuxi, Jiangsu 214122, People's Republic of China.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Jiang
authors.affiliation: The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University , 1800 Lihu Road, Wuxi, Jiangsu 214122, People's Republic of China.
authors.forename: Zhenggang
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Department of Chemistry, University of Hull , Hull HU6 7RX, United Kingdom.
authors.forename: Bernard P
authors.initials: BP
authors.lastname: Binks
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D013501:Surface-Active Agents; D012822:Silicon Dioxide