A paper published in JCIS Open explores the development of a Hydrophilic-Lipophilic Difference (HLD) model for cationic ammonium surfactants. According to the authors, the HLD can be described by additive contributions to account for oil and surfactant nature, temperature, ionic strength, etc., but without the addition of alcohols, the model is incompatible with cationic surfactants; it is better suited to anionic and nonionic surfactants.
See archived: [video] Student Poster; Alternative to HLB
The present work proposes a system based on a blend of single-tailed and double-tailed cationic surfactant to study the oil contribution, from which the surfactant contribution is derived via an experimental approach: HLD-titration. Considering the variables unique to cationic surfactants and incorporating calculations detailed in the open access article, for the first time, the authors could successfully introduce cationic surfactants into the HLD framework without the complication of cosurfactants.
See archived: Comparatively Speaking; HLB vs. PIT