Исследование гелей с карбомерами методами ротационной вискозиметрии и спиновых зондов

The rheological properties of gels with carbomers and polycarbophils have been studied as dependent on pH, concentration and type of carbomer, temperature, and composition of the dispersion medium. Using the obtained results it is possible to make a reasonable choice of carbomers as gel forming agents. Gelation resulting from the neutralization of a carbomer by alkali does not increases the viscosity of a dispersion medium of the gels. Spin probes dissolved in the medium on a micro level are in the state of fast isotropic rotation, which ensures rapid and complete release of active substances dissolved in such gels. In contrast, the correlation time of rotational diffusion (τ –1 ) of 4-amino-TEMPO probe in gels passes through a maximum at pH 7.1 – 8.7, which is probably due to the interaction of a cation that is formed upon protonation of the amino group of this spin probe with several neighboring carboxylate anions of the carbomer. An increase in the temperature leads to a decrease in this effect, while the introduction of ethanol and N -methylpyrrolidone into the gel leads to enhancement of this effect. These interactions can decrease the release of some active substances and reduce or prolong the efficacy of their pharmacological action.