In this thesis we will present the results obtained in a research project aimed at using EPR spectroscopy to determine the kinetic properties of reactions takfug place at the interface between H20 and an amphiphilic supramolecular ag~egates. The choice of EPR spectroscopy is related mostly to its high sensitivity (the absolute EPR lower limit is around 10-12 M of spins). The possibility to measure the diffusion parameters and flexibility of the molecules making up the amphiphilic aggregate was also anothe[ aspect that appe.aled to us: . it was possible, in a single experiment, to determine a series ofdata that would have required at least two separate spectroscopic methods to access. Chapter I reviews all the relevant literature in the EPR field as well as of phospholipid membranes and their characteristics with a particular attention on the reactions taking place at the H20/amphiphilic aggregate interphase. The design and preparation of the molecules involved in this investigation is discussed in Chapter IT along with the characterization of the model molecules used for the optimization of the synthetics passages involved in the prepar~tion of the spin probes employed in the subsequent analyses. In Chapter III the problem of the characterization of the liposomes is addressed. Dynamic Light Scattering and EPR line shape simulation results are presented along with cw-EPR biradical distance measurement procedures for the determinati~n of the distance between the two nitroxides embedded in the hydrophobic phase. The kinetic analyses -for the thiol-disulphide exchange reaction are discussed in Chapter IV. Preliminary studies for the optimization of the analytical protocol are presented for the reaction taking place in homogenous phase in MeOH and in the presence of phospholipid amphiphilic aggregates. Along with the data collected for egg yolk phosphatidylcholine with a 0-1 molar ratio ofcholesterol, systems employing micelles and synthetic phospholipids are presented in various conditions of pH. All kineti~s were recbrded under pseudo 1st order conditions using different concentrations of2-mercaptoethanol. Chapter V describes the results obtained using spin labels in the characterization of organogelators. Monoradical and biradic~l systems were employed in order to compare the different kinds ofinformation from these two different nitroxide systems. In Chapter VI all the experimental procedures are reported along with the corresponding characterization for the target molecules prepared.