α-Gel (α-Form Hydrated Crystal) Prepared by Eco-Friendly Cationic Surfactant.

We studied the structures and properties of gel samples prepared by mixtures of N-[3-(dimethylamino)propyl]docosanamide (APA-22) acid salt (APA-22 L-lactic acid), 1-octadecanol (COH), and water. The gel samples prepared at the mole ratios [APA-22 L-lactic acid]:COH = 1:3, 1:4, and 1:5 yielded two phases; one being the α-gel (α-form hydrated crystal) phase, incorporating a significant quantity of water between lamellar bilayers, and the other being the excess water phase. The lamellar d-spacing remained practically unaltered at these mole ratios, thus maintaining the quantity of water incorporated between the lamellar bilayers relatively constant. Starting at 30°C, the gel samples transformed into a lamellar liquid crystal phase at high temperatures (85°C) and a β-gel phase at low temperatures (5°C). Interestingly, following dilution by pure water, the viscosity of the gel samples decreased with increasing COH content. We expect that the viscosity change affects the performance of the gel samples as hair conditioners.