The present thesis deals mainly with the systematic broadband dielectric relaxation spectroscopy (DRS) of choline, 2-hydroxyethyltrimethylammonium ion, based electrolytes and surfactants. DRS have been performed for aqueous solutions of choline chloride (ChCl), chlorocholine chloride (Cl-ChCl) and ammonium chloride (NH4Cl) over a wide range of frequencies (0.2 ≤ n / GHz ≤ 89) up to reasonable concentration range of each salt at 25°C. The spectra were best described by a superposition of three Debye processes (3D model), except for NH4Cl at c > 1.10 M which is best fitted with a 2D model. The mode centred at ~18 GHz can be assigned to bulk water relaxation. In aqueous ChCl and Cl-ChCl the relaxation process centred at ~12 GHz is assigned to be a composite mode arising due to the incidentally overlapping relaxations of water molecules with reduced dynamics (‘slow water’) hydrating the cations and of the reorienting Ch+ and Cl-Ch+ ions in respective systems. For NH4Cl(aq), however, this intermediate mode is assigned solely to the slow water molecules. The lowest frequency relaxation process detected at ˂1 GHz (in all studied salts) is fairly assigned to the ion-pair and/or ion-cloud relaxation. From the amplitudes of bulk and slow water modes effective hydration numbers of the cations were determined. Both Ch+ and Cl-Ch+ bind ~5 H2O molecules irrotationally at infinite dilution, whereas it turned out that NH4+ ion does not ‘freeze’ water molecules in its vacinity. At infinite dilution, ~18, ~22 and ~13 H2O molecules are found to be slowed down by Ch+, Cl-Ch+ and NH4+ ions, respectively. For the investigations of micellar systems aqueous solutions of two bio-compatible surfactants, namely choline dodecanoate (ChC12) and choline dodecylsulfate (ChDS), and sodium dodecanoate (NaC12) have been studied over a frequencies range of (0.01 ≤ n / GHz ≤ 89) at 25°C. Theory of Grosse have been used to model the dielectric properties of above mentioned colloidal solutions. DR spectra of all studied surfactants were best fitted by a superposition of four Debye (4D) processes. The two low frequency processes, peaking at ≤ 0.1 GHz and ≤0.4 GHz are micelle-related. They can be assigned to the fluctuations of the diffuse ion cloud surrounding the micelle and to the tangential motions of bound counterions, respectively. By applying the Grosse model the distance, RG, of the bound counterions from the micelle centre, the volume fraction of the micelles, mic, and their surface conductance, s, were determined. By rationalizing the Grosse’s parameters it appeared that for NaC12 and ChDS micelles, counterions are directly attached on the micellar surface while in case of ChC12 counterion-headgroup interactions are weak and are water mediated.The relaxation centred at ~20 GHz is due to bulk water. The mode peaking in the range 6 < n / GHz < 9 is regarded as a composite (in ChC12 and ChDS) originating from the incidentally overlapping relaxations of ‘slow’ water molecules hydrating the micelles and their counterions and of the choline cations themselves, whereas in NaC12 this mode is assigned to slow water relaxation. In ChC12(aq) system no irrotational bounding is observed for carboxylate headgroup, whereas in NaC12(aq) and ChDS(aq) micelles, per headgroup, ~5 and ~2.5 H2O molecules are ‘frozen’, respectively. The obtained numbers of slow H2O molecules, per headgroup, were found to be ~18, ~18 and ~50 for ChC12(aq), ChDS(aq) and NaC12(aq), respectively
