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In the context of environmental concerns for the production of surface active species, the introduction of a carbonyl function into the skeleton of ethyleneglycol-derived solvo-surfactants is a way to access cleavable compounds with presumed enhanced biodegradability. Ethylene glycol monobutyrate (C(3)COE(1)) was synthesized and compared to its ether counterparts, ethylene glycol monopropyl (C(3)E(1)) and monobutyl ethers (C(4)E(1)), to assess the effect of the insertion of a carbonyl function in the skeleton of short-chain ethoxylated amphiphilic compounds. In aqueous solutions, the ester has intermediate behavior between that of the two ethers with regard to surface tension, solubilization of Me-naphtalene in water, and self-diffusion by PGSE NMR. In ternary systems, C(3)COE(1) and C(3)E(1) have the same optimal oil (EACN = 2.8), which is much more polar than that of C(4)E(1) (EACN = 8.5). With regard to the ability to form structured systems, the behavior in water does not differ significantly for the three compounds, and the transition between nonassociating solvents and amphiphilic solvents, sometimes called solvo-surfactants, is gradual. In ternary systems, however, only C(4)E(1) and C(3)COE(1) form a third phase near the optimal formulation, which tends to show that C(3)COE(1) possesses the minimum amphiphilicity to get a structuration. Self-diffusion NMR studies of the one-phase domains do not, however, allow us to distinguish between different degrees of organization in the three systems.

The binary phase diagram of tetraethylene glycol decanoyl ester (C9COE4) was investigated in the micellar region by PGSE-NMR (pulse field gradient spin echo nuclear magnetic resonance) and in the lamellar liquid crystalline state by 2H NMR. Its behavior was compared to the ether counterpart, tetraethylene glycol decanoyl ether (C10E4), whose phase diagram is well-described. The determination of the self-diffusion coefficient as a function of concentration permitted not only a determination of the critical micellar concentration (cmc) values but also the determination of the size and shape of micelles formed by both compounds. The evolution of the self-diffusion coefficients in the vicinity of the cloud point was also studied, showing no micellar growth with increasing temperature. 2H NMR analyses at the border of and within the liquid crystalline region gave an insight into the lamellar phase structure. We investigated in detail the lamellar phase of both compounds by comparing the values of quadrupolar splittings (Deltanu) measured under the same conditions. Lower Deltanu values were found for the ester compared to the ether: since the ester probably binds more water than the ether, these lower Deltanu values would indicate a lower order parameter in the liquid crystal phase. NMR techniques, either PGSE-NMR or 2H NMR, were confirmed as useful tools to characterize aqueous phase behavior of surfactants, providing supplementary information to the classical techniques such as visual observations, polarized optical microscopy (POM), and surface tension measurements. They also provide a unique insight into the molecular organization in the different phases formed.