Aqueous self-assembly and physicochemical properties of 1,2-dilauroyl- rac-glycero-3-( Nα-acetyl- l-arginine)

Abstract

Diacylglycerol-amino acid conjugates constitute a novel class of biocompatible surfactants being of great interest both from academic and industrial viewpoints. In this paper, the aqueous phase behaviour of 1,2-di-lauroyl- rac-glycero-3-( N α-acetyl- l-arginine) (indicated as 1212RAc) is investigated by a number of experimental approaches. The phase diagram is dominated by three monophasic regions; an isotropic solution, and two lamellar phases separated by a birefringent biphasic region. At very low concentrations ( C < 1.5 wt.% 1212RAc), the isotropic solution ( Iso) is mainly composed of monodispersed vesicles ( R h ≈ 300 nm). Within the concentration interval 2 wt.% < C < 17 wt.% a dilute lamellar phase ( Lam 1 ) occurs which is thermodynamically stable over a wide T-interval. This turbid phase (slightly birefringent under shaking) seems to consist of close-packed vesicles exhibiting flow properties varying with the composition and the temperature. Above 42 wt.% 1212RAc, a soft birefringent lamellar phase ( Lam 2 ) exhibiting all properties of smectic lamellar structures is observed. The analysis of phase behaviour of 1212RAc/ 2H 2O system is completed by a physicochemical study on the properties of some selected mixtures in the monophasic regions. In this part of the paper, we characterize the thermotropic phase transitions, viscoelasticity and shear flow of Lam 1 , as well as the swelling properties and the water organization in Lam 2 phase.