Co-surfactant properties of ketones

A series of ternary systems water/sodium dodecylsulfate (SDS)/ketone for different ketones ranging from propanone to 2-octanone are studied in some detail as well as the quaternary system water/SDS/2-pentanone/n-dodecane. Phase diagrams, elec. conductivities and one small angle neutron scattering spectrum of these systems are given and compared to corresponding results of systems contg. aldehydes instead of ketones. From this comparison it follows a remarkable analogy between the systems contg. a linear aliph. aldehyde with n-carbon atoms and those contg. 2-ketones with n+1 carbon atoms. It is concluded that the recently suggested co-surfactant behavior of aldehydes can also be discussed for ketones. As far as the elec. cond. is concerned this analogy is also shown for water/AOT/aldehyde and water/AOT/ketone systems

Can aldehydes participate in the nanostructuration of liquids containing charged micelles?

The phase diagrams of several ternary systems water/sodium dodecylsulfate (SDS)/alkanal are studied as well as the elec. cond. of such systems for various compns. Comparison of the results to those obtained fro the analogous systems water/SDS/alc. shows remarkable similarities. Consequently, one can suppose a similar behavior of alcs. and alkanals in these media. In particular, it is probable that long-chain alkanals act as cosurfactants whereas short-chain alkanals are not favorable for micelle formation. For a particular system: water/SDS/pentanal and the corresponding system: water/SDS/1-pentanol small-angle neutron scattering expts. yield further arguments for this interpretation

Comparison of enzymic activity and nanostructures in water/ethanol/Brij 35 and water/1-pentanol/Brij 35 systems

The kinetics of enzyme-catalyzed alc. oxidn. has been measured in liq. water/ethanol/Brij 35 and water/1-pentanol/Brij 35 systems, essentially in the water-rich regions. For the ethanol systems it was found that the enzymic activity sharply decreases with increasing alc. concn. independently of the surfactant concn. between 0 and 22 mass %. In the case of the 1-pentanol systems the enzymic activity decreases also with increasing alc. concn., but this decrease can considerably be attenuated by adding increasing amts. of surfactant. To explain these results at the nanometer level, small-angle neutron-scattering (SANS) expts. have been carried out on these systems. The comparison of the scattering and the kinetic measurements suggests the following interpretation. In all cases, the enzymic activity depends on the concn. of the alc. in the aq. phase or in the aq. pseudophase contg. the enzyme. A certain amt. of alc. may be present in an org. pseudophase formed by direct micelles. In the case of the 1-pentanol systems the alc. participates in the structuration of the micelles and is concd. in the micelles, whereas in the case of the ethanol systems the alc. remains essentially in the aq. pseudophase and even destroys the micelles. These results suggest that in some cases enzymic activity can be used as a probe to detect some aspects of the mol. organization of a complex liq

Small angle neutron scattering of D2O-Brij 35 and D2O-alcohol-Brij 35 solutions and their modelling using the Percus-Yevick integral equation

Small angle neutron scattering of direct micelles in binary surfactant-D2O and ternary surfactant-alc.- D2O systems was measured. The nonionic surfactant was poly(oxyethylene-23) lauryl ether (C12E23, com. name: Brij 35) which was used at concns. far beyond its crit. micellar concn.: between 0.1 and 15% (∼1.0 × 10-3-1.5 × 10-1 mol L-1). The alcs. were butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol at concns. of ∼0.25 mol L-1. The spectra could quant. be modeled by the Percus-Yevick integral equation method in combination with a core/shell model yielding detailed information about the size, the (ellipsoidal) shape, the aggregation no., the internal structure and the distribution of the micelles. The ternary systems were modeled with an addnl. parameter, the partition of the alc. between the outer aq. bulk and the inner micellar pseudo-phase. In the case of the pentanol system the partition coeff. inferred from NMR self-diffusion measurements was used to describe the scattering result