Department of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, 30332-0100 (USA).
Angew Chem Int Ed Engl. 2014 Dec 1;53(49):13385-9. doi: 10.1002/anie.201405816. Epub 2014 Oct 3.
Liquid foams are familiar from beer, frothed milk, or bubble baths; foams in general also play important roles in oil recovery, lightweight packaging, and insulation. Here a new class of foams is reported, obtained by frothing a suspension of colloidal particles in the presence of a small amount of an immiscible secondary liquid. A unique aspect of these foams, termed capillary foams, is the particle-mediated spreading of the minority liquid around the gas bubbles. The resulting mixed particle/liquid coating can stabilize bubbles against coalescence even when the particles alone cannot. The coated bubbles are further immobilized by entrapment in a network of excess particles connected by bridges of the minority liquid. Capillary foams were prepared with a diverse set of particle/liquid combinations to demonstrate the generality of the phenomenon. The observed foam stability correlates with the particle affinity for the liquid interface formed by spreading the minority liquid at the bubble surface.
液体泡沫在啤酒、泡沫牛奶或泡泡浴中很常见；泡沫在采油、轻包装和保温方面也起着重要作用。本文报道了一种新的泡沫，通过在少量不混溶的二次液相存在下将胶体颗粒悬浮液发泡得到。这些泡沫的一个独特方面，称为毛细泡沫，是颗粒介导的少量液体在气泡周围的扩散。由此产生的混合颗粒/液体涂层可以稳定气泡，防止聚结，即使颗粒本身不能稳定气泡。通过用由少数液体桥连接的多余颗粒的网络捕获来进一步固定涂覆的气泡。毛细泡沫是用各种不同的颗粒/液体组合制备的，以证明该现象的普遍性。观察到的泡沫稳定性与颗粒对在气泡表面形成的少数液体界面的亲和性相关。
