A PH-SENSITIVE HYDROGEL BASED ON POLY(ETHOXY TRIETHYLENE GLYCOL MONOMETHACRYLATE)

Ethoxy triethylene glycol monomethacrylate was synthesized and polymer ized at 80 degrees C in dimethylformamide solution with AIBN as initia tor. Both monomer and polymer were characterized by C-13 n.m.r. spectr oscopy. The analysis of the microstructure of the poly(ethoxy triethyl ene glycol monomethacrylate), PTEG, revealed an isotacticity parameter of 0.24, rather similar to free-radical poly(methyl methacrylate) and other poly(alkyl methacrylate)s. Swelling behaviour of the polymer wa s studied by the immersion of films in water and in buffered solutions at various pH values from 1 to 10. The hydration process was followed gravimetrically and the diffusion of water was analysed on the basis of the stress relaxation model of polymer chains. The results obtained are in good agreement with a second-order diffusion kinetics. A sharp increase of the equilibrium hydration degree between pH 5.5 and 7.4 i s observed. The pH-sensitive transition is reversible, as is shown by the dehydration of swollen gels when they are introduced into acidic s olutions (pH 1-5) after swelling in alkaline media at pH 8-10.