Liquid crystalline phases of linear alkylbenzene sulphonate in spray-dried detergent powders studied by small-angle X-ray scattering, TEM, and ATR-IR spectroscopy

Spray-dried detergent granules have a complex and multi-scale structure, in which submicron sized crystals of inorganic salts along with multi-lamellar stacks surfactant molecules are dispersed within matrix phase. In this study, two model formulations based on sodium linear alkylbenzene sulphonate (NaLAS) sulphate were used to investigate the molecular structure stacked lamellae. The parameters lamellar d-spacing, bilayer thickness (dHH) water layer (dW) determined using small-angle X-ray scattering. Four sets lamellae detected nil-silicate powders conditioned at 33 % RH (relative humidity). exposure these samples higher level (75 %) resulted reduced number coexisting phases by two. This was accompanied an increase d-spacings considerable reduction thicknesses (dHH). explained fluidity disappearance water-poor solid polymorphs. consistent results FTIR for samples, indicating conformational disorder alkyl chains value. Interestingly, presence silicate display greater degree swelling relatively low value (33 RH) as compared those absence silicate. Nonetheless, found slightly decrease %), attributed moisture-induced glass transition kosmotropic effect silicates.