Stabilization of Foams with Inorganic Colloidal Particles

Abstract

Wet foams are used in many important technologies either as end or intermediate products. However, the thermodynamic instability of wet foams leads to undesired bubble coarsening over time. Foam stability can be drastically improved by using particles instead of surfactants as foam stabilizers, since particles tend to adsorb irreversibly at the air-water interface. Recently, we presented a novel method for the preparation of high-volume particle-stabilized foams which show neither bubble growth nor drainage over more than 4 days. The method is based on the in-situ hydrophobization of initially hydrophilic particles to enable their adsorption on the surface of air bubbles. In-situ hydrophobization is accomplished through the adsorption of short-chain amphiphiles on the particle surface. In this work, we illustrate how this novel method can be applied to particles with various surface chemistries. For that purpose, the functional group of the amphiphilic molecule was tailored according to the surface chemistry of the particles to be used as foam stabilizers. Short-chain carboxylic acids, alkyl gallates, and alkylamines were shown to be appropriate amphiphiles to in-situ hydrophobize the surface of different inorganic particles. Ultrastable wet foams of various chemical compositions were prepared using these amphiphiles. The simplicity and versatility of this approach is expected to aid the formulation of stable wet foams for a variety of applications in materials manufacturing, food, cosmetics, and oil recovery, among others.

Porous Ceramics

“…The kinetics of alumina slip swelling for the production of lightweight corundum materials have been investigated [22]. Another method is the impregnation of a polymer cellular matrix with a ceramic suspension and subsequent squeezing out, drying, and thermal treatment to remove the organic components [23]. The addition or embedding of ceramic fibers into the mixture, followed by molding with binders and the subsequent thermal treatment of the molded products, can also yield porous materials [24].…”

Functionalization of Microstructured Open-Porous Bioceramic Scaffolds with Human Fetal Bone Cells

“…[13][14][15][16][17] The adaption of this foaming method allowed the production of macroporous scaffolds which are tailorable not only in pore size, but also in pore interconnectivity. 18,19 In the present study, we made use of this direct foaming method to produce scaffolds from calcium aluminate and evaluated them as potential permanent bone graft materials.…”

“…[10][11][12] In the present study, our goals were to develop calcium aluminate scaffolds suitable for permanent bone replacement, displaying an open-porous channel microstructure allowing the engraftment and migration through the ceramics of human histocompatible bone-derived cells. The calcium aluminate scaffolds were produced from a modified direct foaming method [13][14][15][16][17][18][19] which allows the production of macroporous scaffolds which are tailorable in pore size, microstructure and shape. In particular we aimed to determine the optimal pore sizes to allow survival and migration of these human bone-derived cells across the scaffolds.…”

Electrochemical Insights on the Hydrophobicity of Cellulose Substrates Imparted by Enzymatically Oxidized Gallates with Increasing Alkyl Chain Length

“…Also, some alkyl gallates have proved useful as multifunctional food and pharmaceutical additives by virtue of their anti-browning 7 , antifungal 8 , and antibacterial effects 9,10 . In addition, they have been shown to possess amphiphilic and anticancer properties [11][12][13] . Several studies have employed gallates of variable alkyl chain length to modify the properties of materials such as wool 14 , cellulose 15 , chitosan 16 , titanium dioxide 17 , and ceramics 18 , conferring improved thermal and thermo-oxidative stability (polymers, foams) or dispersibility.…”