Chapter 25 - Lamellar Gel Network

Abstract

​Lamellar gel networks have been used in various cosmetics and pharmaceutical products for many years. A lamellar gel network is a multiphase colloidal structure. The network comprises an Lβ phase, a bulk water phase, and often an oil phase as well. Lβ phase is a lamellar phase built with solid-state surfactants below Krafft temperature at a much higher concentration than the solubility limit. The mechanical strength of the surfactant bilayer is much higher than than that of a liquid crystal. With this property and due to the network structure, a lamellar gel network is essentially stable by physically holding the bulk water and oil phases together, which otherwise immediately phase separate. In cosmetic formulations, the Lβ phase utilizes combinations of fatty alcohols and surfactants. Together, these amphiphiles form a hexagonally packed α-gel structure with the unit crystalline structure of a bilayer. α-Gel has the property of crystalline solidity as the molecules are restricted from relocating one another, although it is not pure crystal as the alkyl chains can still revolve around the alkyl-chain axes. Thus, it is called a gel but not a crystal.