Rheological properties of modified gels and cryogels

Abstract

The paper presents the results of a study of the changes in viscosity during the interaction of an aqueous solution of polyvinyl alcohol with a solution of glyoxal. The three-dimensional structure is formed as a result of the interaction of one aldehyde group of dialdehyde with two hydroxyl groups of polyvinyl alcohol, while the other aldehyde group is bound with the adjacent chain molecule of polyvinyl alcohol. The progress of the acetylation of polyvinyl alcohol with glyoxal was investigated using a rotational viscometer. With an increase in the concentration of glyoxal, an exponential increase in the viscosity of the system occurs, which suggests the appearance of fragments, consisting of numbers of ‘crosslinked’ polyvinyl alcohol macromolecules. They grow in size and increase in the number over time. This process of viscosity increase results in the formation of a continuous spatial polymer network in the entire reaction mixture. Hence, the system loses its fluidity ( δ → ∝), so that a gel is formed. The deformation of crosslinked gels and cryogels obtained after the freezing-thawing cycle was investigated. It was found out that the process of additional cryostructuring of three-component gels improved their elastic properties. By varying the concentration of polymer or glyoxal, gels and cryogels with desired properties may be obtained, which should find application in oil and gas technologies.