Properties of New Magnetic Surfactants

Abstract

This paper describes the synthesis and detailed characterization of a new set of magnetic surfactants containing lanthanide metal counterions. SQUID magnetometry has been used to elucidate the magnetic phase behaviour, and small-angle neutron scattering (SANS) provides evidence of micellar aggregation in aqueous media. This study also reveals that for cationic surfactants in aqueous systems there appears to be no significant increase in magnetic susceptibility after micellization.

Magnetic surfactants

“…The authors then made more MILSs through the metathesis of common cationic surfactants with ferric chloride. Interestingly, at the air-water interface, in the absence of an applied magnetic field, the magnetoresponsive surfactants are more effective than a magnetically inert analogue ( For surfactants based on Ho and Gd even greater responses were observed, though now the compounds were no longer ionic liquid in nature [15]. It should be noted that these measurements were not quantitative.…”

“…By increasing the alkyl chain length of the imidazolium moeity to C10, it was demonstrated that the ionic liquid 1-methyl-trimethylimidazolium tetrachloroferrate (C10mimF) is surface active to generate a magnetic ionic liquid surfactant (MILS) [14,15]. The authors then made more MILSs through the metathesis of common cationic surfactants with ferric chloride.…”

“…It was demonstrated that these new MILSs behaved like conventional surfactants in that they form micelles and various lyotropic mesophases above a critical micelle concentration (cmc) [14,15]. It was attempted to measure the cmc as a function of effective magnetic moment (determined by vibrating sample magnetometer) for a holmium based surfactant [15].…”

“…It was attempted to measure the cmc as a function of effective magnetic moment (determined by vibrating sample magnetometer) for a holmium based surfactant [15]. It was hypothesized that this may look similar to a conductivity versus concentration plot [29], where a change in the gradient may be observed at the cmc due to the partitioning of metal centres near each other once aggregation occurs.…”

“…However, in all cases their intrinsic magnetic sensitivity was largely overlooked. Recently, while investigating magnetic ionic liquid surfactants (MILSs) [13] it was noticed that even dilute aqueous solutions retained a magnetic response and that now surface tension could be modulated in a magnetic field [14,15]. This discovery adds to the armory of responsive stimuli allowing for surfactant properties to be controlled simply by the switching "on" and "off" of a magnetic field.…”