In the recent past the antioxidant properties of vitamin C, vitamin E, and their derivatives have been extensively studied, particularly for their peculiar activity as radical scavengers. Furthermore, the association of vitamin C with vitamin E shows an interesting synergic effect in preventing the oxidation of unsaturated fatty compounds such as linoleic acid, with vitamin C acting as a protective shield for vitamin E in solution against oxidizing agents. Vitamin C derivatives, such as its alkanoyl-6-O-ascorbic acid esters, act even better than ascorbic acid itself, because they possess the amphiphilic structure that allows the molecule to enter the hydrophobic region of a micelle or of a liposome. In order to deepen the understanding of the vitamin C/vitamin E mixed system and of the role played by ascorbic acid in restoring tocopherols, the miscibility properties of ascorbic acid derivatives and of tocopherols need to be studied in all states of aggregation (Langmuir monolayers, micellar dispersions, vesicles). In this paper we report a detailed study of the properties and behavior of monomolecular films of stearoyl-6-O-ascorbic acid (ascorbyl stearate), and α-(±)-tocopherol at different temperatures and pH, and of their mixtures at 20 °C at the gas/water interface. Our results show that ascorbyl stearate produces monolayers with both liquid-expanded and liquid-condensed phases, while α-tocopherol films are in the liquid-expanded phase only. The two pure components are completely miscible at the gas/water interface in all ratios, and indicate the presence of repulsive interactions between the hydrocarbon chains of the surfactants.

Vitamin C acts as a powerful radical scavenger, and can be used as a convenient antioxidant agent in aqueous media. To extend its properties to nonaqueous environments, alkanoyl-6-O-ascorbic acid esters with different chain lengths were synthesized, and their micellar and antioxidant properties were investigated by surface tension, viscosity, light scattering, neutron scattering, oxygen uptake, and UV/VIS spectra. According to our results, octanoyl-ascorbic acid forms nearly spherical micelles in water solutions above a cmc of about 6 × 10-3 mol/L at 30 °C, while decanoyl- and dodecanoyl-ascorbic acid are poorly soluble in water. No matter how long the hydrophobic chain is, all these esters show the same antioxidant activity as vitamin C and other natural products.

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Langmuir monolayers of p-tert-butylcalix[8]arene (CAL8) at the water−air interface were studied as a function of temperature (between 288 and 308 K), of the spreading solvent (benzene, toluene, dichloromethane, chloroform, and carbon tetrachloride), and in a mixture with fullerene C60. Two different mixed systems were studied:  (i) spreading isotherms (surface pressure versus molecular area) after separated spreading of CAL8 and C60 solutions (1/1 molar ratio) and (ii) spreading isotherms of the C60−CAL8 complex obtained from precipitation of freshly prepared and stabilized solutions of the two components in carbon tetrachloride. The results show that, at the water−air interface, CAL8 possesses a perpendicular “pleated-loop” conformation, regardless of the spreading solvent. However, the limiting areas do depend on the nature of the spreading solvent, indicating that the flexibility of the CAL8 backbone is significantly affected by the interactions with the spreading solvent, in analogy with the “memory effect” with the retention of the host conformation, even after the removal of the guest, found for bulk solutions. The complexation of C60 by CAL8 does not modify the calixarene's conformation. Films obtained by spreading equimolar solutions of CAL8 and C60 on the water surface show the same Π/A isotherms of the [C60−CAL8] complex, suggesting the formation of stable CAL8/C60 1/1 complexes at the air−water interface. Electronic spectra performed on Langmuir−Blodgett films and on collapsed material, both transferred on quartz plates, support the presence at the interface of the [C60−CAL8] host−guest system, indicating that the water interface acts as a complexation promoter.