Organic foams stabilized by Biphenyl-bridged organosilica particles

Hypothesis Can surface-active particles be designed à la carte just by incorporating functional groups mimicking the structure of the solvent and gas ? This is based on the idea that, to achieve good foamability, the particle wettability needs to be finely tuned to adjust the liquid-particle and gas-particle surface tensions. In practice, could particles containing phenyl rings and alkyl chains assemble at the air–liquid interface and stabilize foams based on aromatic solvents ? Experiments A library of organosilica particles was prepared by sol–gel synthesis using aromatic organosilane precursors. The particles were characterized by TGA , FTIR and 13 C/ 29 Si MAS NMR. The foaming properties were studied after hand shaking and high-speed homogenization . The influence of particle wettability and solvent properties on foam formation was systematically investigated. A comparison was carried out between biphenyl-bridged particles and various stabilizers on foamability in benzyl alcohol . Findings Biphenyl-bridged particles could stabilize foams in aromatic solvents with a high foam volume fraction up to 96% using Ultra-Turrax. The presence of biphenyl rings and short alkyl chains was crucial for foamability. Organic foams were prepared for aromatic solvents with intermediate surface tension (35–44 mN m −1 ) and contact angle in the range 32–53°. Biphenyl-bridged particles outperformed polytetrafluoroethylene and fluorinated surfactants in benzyl alcohol.