The thesis is devoted to the determination of peculiarities of the influence of anionic and cationic polyions on the protolytic equilibria of chromophores (indicator dyes) in aqueous solutions. The differences in the influence of polyanions, anionic surfactant micelles and fullerene and fullerenol colloidal particles on the acid strength of cationic indicator dyes were investigated.
It was shown that the semidiluted conditions of polyelectrolyte solutions are obligatory for determination of the indices of apparent ionization constants, . The selection of the appropriate polyelectrolyte : dye concentration ratio, P : D, allows avoiding the interfering influence of the metachromasy of dyes. For semidiluted solutions of polyelectrolytes P : D > 100. A set of indicator dyes is examined via the spectrophotometric method in aqueous solutions of poly (sodium 4-styrenesulfonate), NaPSS, with molar weight of 70 103 g mol–1. We have determined the values of a series of dyes of different structure and charge type, neutral red, methyl yellow, rhodamine B, pseudoisocyanine, quinaldine red, and pinacyanol. The values of the indicators are substantially influenced by polyelectrolyte concentration and the ionic strength of solutions. The shifts of as compared with the values in water, , are different for the dyes studied, and qualitatively agree with those observed for the same compounds in micellar solutions of anionic surfactant sodium dodecylsulfate, NaDS. The effects are, however, less expressed than in NaDS micelles. This is in line with (i) less negative zeta-potential of the NaPSS coils as compared with that of the NaDS micelles at the same ionic strength of the bulk phase and (ii) the lack of the hydrocarbon core in the case of the pseudophase of this polyelectrolyte. The strong differentiation of acid-base properties of anionic chromophores, particularly sulfonephtalein dyes, is revealed in solution of cationic pH-dependent polyelectrolytes poly (hexamethylene guanidine hydrochroride) and poly (diethyleneamine guanidine hydrochroride) at pH < 7.
The approach to estimate the surface charge density and the degree of counter-ion binding by colloidal particles based on determination has been developed for mixed NaDS – alcohol micelles. As alcohols, 1-butanol and 1-pentanol were used. Whereas the slope of the dependence of neutral red vs. allowed estimating the degree of counter-ion binding in entire SDS micelles, = 0.71 ± 0.02, the corresponding value = 0.39 ± 0.03 at 0.80 M 1-butanol indicates the decrease in the interfacial concentration of the anionic head groups within the Stern layer. The study of salt effects allows estimating value by the polyions. In accord with Manning’s theory, this parameter appeared to be constant and is within the range of 0.6 0.8, similar to that in NaDS micelles.
The acidic strength of indicator acid in fullerene-based aqueous solutions significantly depends on the concentration of pseudophase C60 or C60(OH)18-22, which aggregates have the negative surface potential too as surfaces of polyanions or anionic surfactant micelles. The ζ-potential of both fullerene C60 and fullerenol C60(OH)18-22 aggregates is of about – 25 mV.
