Giulia Capuzzi

Self-assembling and antioxidant activity of some vitamin C derivatives

Abstract Vitamin C behaves as a very powerful radical scavenger in aqueous media and can be successfully used to prevent peroxidation of important unsaturated organic molecules. Its hydrophobic derivatives (i.e. alkyl-esters and ethers) perform the same antioxidant activity in self-assembled structures such as micelles and microemulsion systems. In this work the study on the micellar properties obtained from these hydrophobic derivatives by viscosity, light-scattering, and small-angle neutron-scattering (SANS) experiments, and a comparison between the antioxidant activity of the vitamin C derivatives and the most common natural antioxidants are reported.

Counterion complexation of calixarene ligands in monolayers and micellar solutions

Abstract Calix[n]arenes and their derivatives are currently the object of several studies, due to their peculiar cavity, that is suitable for very specific and efficient complexation of ions and small organic molecules, with a high degree of efficiency and selectivity, and form host–guest systems in the solid and in the liquid state. Besides some very important applications as ion carriers and cages, they can be used for studying the counterion distribution in micellar aggregates formed by anionic amphiphiles such as alkyl-sulfates. In this paper we report the studies on the complexing properties of a new calixarene derivative, namely the 1,3-dioctyloxy-calix[4]arene-crown-6-ether (CAL), that shows a high selectivity for cesium ions, at the air/water interface and in aqueous micellar solutions of cesium dodecyl sulfate. Langmuir surface pressure (π/A) isotherms were performed in order to study the stability of CAL films and the effect of cesium and potassium ions on the monolayer properties. In addition, small-angle neutron-scattering (SANS) experiments were carried out in order to determine the structure of the micellar system, and the interactions between the ligand and the micellar interface. Our study shows that the charge screening at the micellar interface is the predominant phenomenon that rules over the ion transport across liquid membranes, that is usually performed by macrocyclic ligands.

Modulation of interfacial properties of functionalized calixarenes

Calix[n]arenes and their amphiphilic derivatives act as strong ligands, by selectively binding cations and small organic molecules (such as chloroform, toluene, fullerene). The presence of a cavity and of specific electron donor sites results in their ability to form stable host—guest systems with electron-acceptor molecules. We report our studies on the interfacial properties of amphiphilic calixarenes, both at the liquid/liquid and at the air/liquid interfaces, and their selective complexation of alkaline cations and small organic molecules, by performing Langmuir isotherms and small-angle neutron scattering experiments. Changing the guest species, the functional groups, and the experimental conditions (such as temperature, concentration, and ionic strength) can efficiently modulate the interfacial properties of these amphiphilic ligands.

Complexation properties of 1,3-dialkoxycalix[4] arene-crown derivatives: a SANS study

Abstract Calix[4]arene-crown ethers show strong affinity and high selectivity toward alkali, alkaline earth, and transition metal ions. We synthesised 1,3-dialkoxycalix[4]arene-crowns-6 (CAL). This compound presents high selectivity for Cs cations. Small-angle neutron-scattering (SANS) experiments have been performed on micellar solutions of cesium dodecylsulfate in the presence of the calixarene as a function of ligand-to-surfactant mole ratio. From the analysis of the experimental data, the micellar structure, the partition of the calixarenes at the micellar surface and the intermicellar interactions have been determined.