Corroboration of Micellization Behavior in a Series of Quaternary Cationic Surfactants With Atomistic Insight and Biocidal Activity

ABSTRACT Our study investigates the micellization of the selected two‐homolog series of single‐chain cationic surfactants (CS): C n PyBr (1‐alkylpyridinium bromide) and C n TABr (1‐alkyltrimethylammonium bromide) with varying chain lengths ( n = 8, 10, 12, 14, and 16) in an aqueous environment. Interfacial parameters were obtained using the tensiometric method, expressed in terms of critical micelle concentration (CMC), effectiveness ( γ CMC ), surface pressure ( π CMC ), cross‐sectional surface area ( A min ), and maximum surface excess ( Г max ) at 30°C. This study presents atomic insights employing density functional theory (DFT) calculations for the examined CS series using Becke's three‐parameter Lee‐Yang‐Parr (B3LYP) method and the 3‐21G basis set. Various optimized descriptors such as ionization potential (IP), electron affinity (EA), global hardness (GH), and global softness (GS) were derived from the highest occupied molecular orbital ( E HOMO ) and lowest unoccupied molecular orbital ( E LUMO ) energy values. The solution behavior of C 16 PyBr and C 16 TABr displayed varied textures, viz., fluid, soft gel, and hard gel. Also, their biocidal activity in terms of zone of inhibition (ZOI) and minimal inhibitory concentration (MIC) was assessed against bacteria and fungi. Additionally, a quantitative structure–activity relationship (QSAR) for the C n PyBr and C n TABr series was established with the intent to corroborate the antimicrobial performance with the CMC of the examined CS.