Investigation of copolymers based on unsaturated polyester resins

Abstract

The possibility of controlling the properties of network copolymers of polyethylene glycol maleate by changing external factors (pH of medium, temperature, the presence of organic solvents and low molecular weight inorganic salts) has been studied. Swelling capacity of the copolymers investigated was studied using gravimetric method. It has been established that the hydrogels are sensitive to the change of pH of medium and the copolymers’ samples undergo reversible swelling-collapse-swelling transfer. Basic factors which determine the swelling of the gels studied are electrostatic repulsion of similarly charged carboxylic groups and appearance of opposite charges on macrochains as a result of the hydrolysis of acrylamide segments. It has been shown that the hydrogels of polyethylene glycol maleate with acrylamide are sensitive to the influence of temperature and the dependence of the swelling degree has extreme character. The sensitivity of the copolymers to the presence of low molecular salts has been established. Combined regimen of their behavior in the presence of salts is due to the hydrolysis of amide bond in the segments of the copolymer of polyethylene glycol maleate. When adding organic solvent to the medium which is the polymer swollen in water continuous contraction of the samples studied is observed and it leads to the shrinkage of the hydrogels’ size. Suppressive action of organic solvents on swelling of the copolymers of polyethylene glycol maleate with acrylamide is explained by the polarity of the solvents.