Lysine-based oligomeric surfactants with cyanuric chloride: synthesis and micellization properties

Abstract

Two lysine-based oligomeric surfactants 2C 12 LyNa 2 and 3C 12 LyNa 3 were synthesized using cyanuric chloride and N ε -lauroyl-L-lysine. Their physicochemical properties of aqueous solutions were determined by surface tension and conductivity as well as dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. From the results of surface tension and conductivity measurements, the critical micelle concentration decreases by one order of magnitude with increasing degree of oligomerization. 3C 12 LyNa 3 and 2C 12 LyNa 2 tend to form premicellar aggregates in solution at a sufficiently low concentration. In addition, their interface behaviors such as adsorption and micellization are reflected by parameters such as the minimum surface area per molecule (A min ), adsorption efficiency and effectiveness (pC 20 ), maximum surface excess concentration (Γ max ), and standard free energy for micellization and adsorption (ΔG mic ∘ , ΔG ads°) . The A min value of 2C 12 LyNa 2 and 3C 12 LyNa 3 is two times that of the monomeric surfactant sodium N ε -lauroyl-L-lysine (C 12 LyNa). With increasing degree of oligomerization, pC 20 increases, which follows the reverse order for ΔG mic°a nd ΔG ads°. TEM results showed that C 12 LyNa forms slightly entangled rod-like micelles. 2C 12 LyNa 2 and 3C 12 LyNa 2 can self-assemble into regular spherical assemblies; DLS showed that with increasing degree of oligomerization for 2C 12 LyNa 2 and 3C 12 LyNa 3 , the diameters of the spherical aggregates decrease and the hydrophobic interaction and hydrogen bonding become stronger.

Rheology of novel photosensitive viscoelastic trimeric cationic surfactant/trans‐ortho‐methoxycinnamic acid micellar solutions

“…Raghavan's group was the first to construct a light‐induced thinning micellar solution composed of CTAB/ trans‐ OMCA and a light‐induced thickening micellar solution composed of erucyl dimethyl amidopropyl betaine (EHAC)/ trans‐ OMCA (Ketner et al, 2007; Kumar & Raghavan, 2009). Generally, there are many outstanding advantages of oligomeric surfactants compared with traditional surfactants, such as high surface activity (Yoshimura et al, 2003), lower critical micellar concentration (Liang et al, 2015), and greater aggregation ability (Kusano et al, 2012), which attracts increasing interest. The structural diversity and rich aggregation behavior of Gemini surfactants provide a prerequisite for constructing novel photo‐responsive micellar solutions.…”