The mixed micelles C12E4 (tetraethylene glycol mono-n-dodecyl ether)/CTAB (hexadecyltrimethylammonium bromide) were studied. The surface tension results were analyzed on the basis of a treatment that considers the relation between the activity coefficients according to the Gibbs−Duhem equation. The results are compared with Rubingh's treatment, which considers the activity coefficients given by the regular solution theory. The conductivity of the samples and the aggregation numbers at low mixture concentration are also given.

The rheological properties of different phases of the CTAB/benzyl alcohol/water system have been studied. The L phase, except the samples close to the hexagonal liquid crystal, is a viscous fluid with a characteristic Newtonian behavior. On the contrary, the L phase samples close to the hexagonal phase are pseudoplastic fluids built up of cylindrical micelles with elastic properties. The hexagonal liquid crystal behaves as a shear thinning fluid with a well-defined zero-shear-rate viscosity, while the lamellar liquid crystal does not show a zero-shear-rate viscosity and it presents yield stress values. Both liquid crystals have significant elastic properties although we could not find any linear region of viscoelasticity in the lamellar phase. The cubic liquid crystal is also an elastic phase with ringing gel properties. The hexagonal and cubic liquid crystals follow the Maxwell treatment only at low angular frequencies. Consequently, from the results the relaxation time and the instantaneous elastic modulus have been obtained. The relaxation times range in these phases from 2 to 9 s while the relaxation times of the cylindrical micelles are three decades smaller. LA9515682

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PNIPAM hydrogels functionalized with gold nanoparticles were prepared by making use of catechol redox chemistry. For this purpose catechol groups were introduced in the PNIPAM network during the cross-linking polymerization process (PNIPAM–catecholx hydrogel). These groups act as reducing agents of HAuCl4, which enables the functionalization of the PNIPAM with gold nanoparticles (PNIPAM–catecholx@Au hydrogel). The rheological study shows that catechol groups reinforce the hydrogel structure. A stronger effect was observed after the functionalization of the hydrogel with gold nanoparticles. This influence could be easily observed since the variation of G′ with the MBA mole fraction was fitted to a power-law expression G′ ∼ x MBA a , with a = 1.6 for PNIPAMx hydrogels, a = 2.3 for PNIMPAM–catecholx hydrogels and a = 3.2 for PNIMPAM–catecholx@Au hydrogels. The capability of the PNIPAM–catecholx@Au hydrogel to act as a tunable catalyst was demonstrated with a model reduction reaction. The half-lifetime at 25 °C was 10.5 min; however, at 38 °C the half-lifetime was 133 min.