Synthesis and physiochemical properties of novel gemini surfactants with phenyl-1,4-bis(carbamoylmethyl) spacer

Abstract

A series of novel gemini surfactants, namely, phenyl-1,4-bis[(carbamoylmethyl) N,N-dimethylalkyl ammonium chloride)] (a, b and c), was synthesized systematically and characterized by FTIR, ¹H NMR, ¹³C NMR and MS. The surface and bulk properties were evaluated by surface tension, conductivity, viscosity, dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. These surfactants have been found to have low surface tension (γ_CMC) values as compared to other categories of gemini cationic surfactants, and they form vesicles in solutions at low concentrations. The DLS and TEM studies showed that the aggregations of the above mentioned surfactants changed from larger globular vesicles and smaller globular micelles to network aggregates and then to globular vesicles with an increase in the surfactant concentration. It is assumed that this unusual aggregation behavior is related to the transformation of the molecular conformation of phenyl-1,4-bis(carbamoylmethyl) spacer, along with its rigidity and hydrogen-bonding capability. The thermodynamic parameters of micellization process, namely, standard Gibbs free energy (ΔG⁰_m), enthalpy (ΔH⁰_m) and entropy (ΔS⁰_m), were derived from conductivity measurements at different temperatures. The Krafft points of three gemini surfactants are very low.