Mária Azori

Physico-chemical studies of polymeric carriers: 2. Molecular mass determination of poly(N-vinylpyrrolidone-co-maleic acid) fractions

SummaryCritical interpretation of the various conceptions concerning the problems in characterization of linear polyelectrolyte type polymers containing maleic acid as a comonomer is given. Proper conditions to avoid the fundamental experimental difficulties are proposed. Our conception is supported by molecular light scattering measurements of hydrolysed, fractionated poly (N-vinylpyrrolidone-co-maleic anhydride) samples. It was found that the problems were eliminated by the reduction of the degree of dissociation of carboxyl groups to a minimum value.

Analysis of the role of complex in the alternating copolymerization of N-vinylpyrrolidone and maleic anhydride

SummaryHeterogeneous copolymerization of 1-vinyl-2-pyrrolidone (NVP) and maleic anhydride (MA) initiated with AIBN was studied in benzene at 60 °C, at two different total monomer concentrations. The existence of a charge transfer complex between the comonomers has been shown and its equilibrium constant determined. The chemical composition of the copolymer was examined as a function of the initial monomer ratio, and it was found nearly equimolecular in a wide range of relative monomer concentrations. Studying the dependence of the initial rate of copolymerization (W0) on the monomer composition, significant increase in W0 was found at a mole ratio of NVP/MA=1 when 3 mol· dm−3 total monomer concentration was applied. The compositional equation for the NVP/MA copolymerization system was derived with the consideration of the effect of complex.

ESR study of γ-irradiated nylon-6; conformational isomerism of free radicals☆

Abstract The ESR spectra of free radicals produced by low temperature γ-irradiation of nylon-6 fibres were studied. The spectra revealed a reversible transformation when the temperature was rapidly changed from liquid nitrogen to room temperature, and vice versa. This transformation was explained in terms of a radical with two conformational isomers, where the isomers can be approached by resonance structures—(CH2)4CHONH and -(CH2)4CHCO-NH- at liquid nitrogen and room temperature, respectively.

Physico-chemical studies of polymeric carriers

SummaryDensitometric conformational studies were made on poly(1-vinyl-2-pyrrolidone-co-maleic acid) in the presence of LiCl, NaCl, KCl, CaCl2, and MgCl2, in order to control ion-binding of the polyanion in dilute aqueous solution. Experimental verification of principal role of deprotonation in the conformational transition of the polyacid chains during titration is given. Correlation was found between the apparent molar volume of the copolymer and the ionic radius of the bound cation.

Investigation of the macromolecular stable free nitroxide radical

Abstract Polystyrene containing t -butyl nitroxide groups was prepared via polymer-analogous reactions and characterized by ESR measurements. Polymerizations of MMA and styrene initiated by AIBN at 50° have been investigated in the presence of the polymeric radical samples. A definite inhibiting effect was observed without retardation of the polymerization of either monomer. A linear relationship was found between the concentration of the polymeric inhibitor and the inhibition period.

Contribution to physiological properties of poly(N-vinylpyrrolidone-alt-maleic acid), toxicity and hemagglutination tests

Acute toxicity of the copolymer of poly(N-vinylpyrrolidone-alt-maleic acid) is examined by two routes of parenteral administration. The effect of prolonged daily treatment of animals, the results of hemagglutination tests of the original, and the modified copolymer as polymer drug models are discussed.

Physico-chemical studies of polymeric carriers - 6. Ultracentrifugal molecular weight determination of a polyacid

SummaryUltracentrifugal studies were made on poly/1-vinyl-2-pyrrolidone-co-maleic acid/ samples eliminating the polyelectrolyte character of the polyacid. Molecular weight values were evaluated from sedimentation-diffusion equilibrium measurements. Good correlation was found between weight average molecular weight values obtained from the equilibrium measurements and those evaluated viscometrically, applying the Mark-Houwink equation determined earlier.

Inhibition effect of polymeric nitroxide on radical polymerization

Inhibition kinetics of MMA and styrene polymerization, initiated by AIBN at 50°C was investigated using a stable polyradical, polystyrene containing t-butyl nitroxide groups, as inhibitor. A definite inhibition effect and a linear relationship between the concentration of polymeric inhibitor and the inhibition period was found.AbstractКинетика ингибирования полимеризации ММА и ститола, инициированной динитрилом азоизомаслянной кислоты при 50° C, была исследована при использовании стабильного полирадикала—полистирола, содержащего трет-бутилнитроксильные группы—как ингибитора. Наблюдалось действительное ингибирование и была найдена линейная зависимость между концентрацией полимерного ингибитора и периодом ингибирования.