Viscosity of associated mixtures approximated by the Grunberg-Nissan model

Previous experiments demonstrated that microheterogeneities occur in liquid systems (2-methylpyridine or 2,6-dimethylpyridine) + water. They are most probably due to the association of the hydrates through hydrogen bonds between water molecules. Substitution of methanol for water causes that the mixtures become homogenous. The results of viscometric studies reported in this study confirmed that the molecular clusters in aqueous solutions are much larger than the complexes occurring in the methanolic systems. Taking into consideration “kinetic entities” rather than monomeric molecules, the dependence of viscosity on concentration and temperaturę have been satisfactorily approximated by the Grunberg-Nissan relation with two adjustable coefficients. The kinetic entities were trimers of water, dimers of methanol, and monomeric amines. The same approach proved to be valid for the activation energy of viscous flow as well

Viscosity of associated mixtures approximated by the Grunberg-Nissan model

Previous experiments demonstrated that microheterogeneities occur in liquid systems (2-methylpyridine or 2,6-dimethylpyridine) + water. They are most probably due to the association of the hydrates through hydrogen bonds between water molecules. Substitution of methanol for water causes that the mixtures become homogenous. The results of viscometric studies reported in this study confirmed that the molecular clusters in aqueous solutions are much larger than the complexes occurring in the methanolic systems. Taking into consideration “kinetic entities” rather than monomeric molecules, the dependence of viscosity on concentration and temperaturę have been satisfactorily approximated by the Grunberg-Nissan relation with two adjustable coefficients. The kinetic entities were trimers of water, dimers of methanol, and monomeric amines. The same approach proved to be valid for the activation energy of viscous flow as well

The influence of crown ether and alcohol on unsaturation and molar mass of poly(propylene oxide)s prepared by use of potassium t-butoxide: reinvestigation of chain transfer reactions

Potassium t-butoxide dissolved in tetrahydrofuran effectively initiates homogeneous polymerization of propylene oxide at room temperature. Unsaturation and molar mass (M n) of the polymers prepared depend on the presence of additives, such as macrocyclic ligand 18-crown-6 (L) and t-butanol. Application of the ligand alone results in distinct increase of unsaturation and decrease of M n, whereas use of t-BuOH leads to simultaneous decrease of unsaturation and M n. Activation of t-BuOK/t-BuOH system with the ligand causes further decrease of unsaturation, that is, from 12.0 to 3.5 mol % for OK/OH (1/3) and OK/OH/L (1/3/2) systems, respectively. Unexpectedly, M n of the polymers obtained does not practically change (4800). This result differs from that reported earlier for neat PO polymerization initiated potassium 1-methoxy-2-propoxide/1-methoxy-2-propanol, in which in the presence of the same ligand M n increases to 12 400 for the same ratio of reagents. The mechanism of studied processes was discussed

Alginate biopolymer coatings obtained by electrophoretic deposition on Ti15Mo alloy

In this work, the electrophoretic deposition method has been developed for the fabrication of bioactive alginate coatings on the surface of Ti15Mo implant alloy. Thin ZnO lm was deposited cataphoretically as the interlayer prior to anaphoretic deposition of alginate (Alg) which was performed from aqueous solution containing 1 g dm3 of NaAlg at room temperature. The deposition voltage and time varied in the range 20 50 V and 30 120 min, respectively. The microstructure of Alg coatings was studied by scanning electron microscope, and the surface roughness was analysed using atomic force microscopy. Structure was studied by grazing incidence X-ray di raction. Chemical composition and functional group were examined using energy dispersive spectrometry and attenuated total re ectance Fourier transform infrared spectroscopy methods, respectively. It was found that controlling the deposition conditions it is possible to obtain amorphous Alg coatings of variable thickness and porosity. Mechanism of electrophoretic deposition of bioactive Alg coatings on the Ti15Mo alloy surface was discussed