Gelling nature of aluminum soaps in oils

Aluminum soaps are notable for their ability to form soap-hydrocarbon gels of high viscosity. For more than half a century, it has been believed that the gelling mechanism is due to a formation of polymeric chains of aluminum molecules with the aluminum atoms linking along the axis and with the fatty acid chain extended sideways. Here we report results from an investigation using high-resolution electron microscopy and rheology measurements that clearly resolve the ambiguity. Our results reveal that the gelling mechanism stems from the formation of spherical nano-sized micelles from aluminum soap molecules, and those colloidal micelle particles then aggregate into networks of highly fractal and jammed structures. The earlier proposed polymer chain-like structure is definitely incorrect. The discovery of aluminum soap particles could expand application of these materials to new technologies.

Graphical abstractThis work demonstrates that aluminum soaps form spherical micelles in oils and that the aggregation of these micelles forms a network that gives rise to the gel formation—thereby refuting a long-held belief that the gel formation was the result of linear polymeric chains of aluminum association.Figure optionsDownload full-size imageDownload as PowerPoint slide