engleski

Biodegradable hydrogels based on poly(vinyl alcohol)-graft-[poly(D, L-lactide)/poly(D, L-lactide-co-glycolide)]

In this work a synthetic procedure is described towards a class of poly(vinyl alcohol)-graft- [poly(D, L-lactide)/poly(D, L-lactide-co-glycolide)] copolymers which are sensitive to hydrolysis and therefore can be used for the development of controllably biodegradable hydrogels. Poly(D, L-lactide) and poly(D, L-lactide-co-glycolide) with various composition were obtained by reacting 2-hydroxyethyl methacrylate with D, L-lactide or glycolide dimers, followed by the transformation of the terminal hydroxyl group into carboxylate with the assistance of succinic anhydride. Coupling of those polyesters (PES) onto poly(vinyl alcohol) (PVA) was performed via the carboxylate group in dimethyl sulfoxide using N, N-carbonyldiimidazole. The graft copolymers were crosslinked via the methacrylate groups using a free radical initiator.The resulting copolymers, in the course of synthesis, were characterized with respect to their molar composition by means of 1H NMR spectra. Furthermore, polymer networks were detected and studied qualitatively by means of IR spectroscopy. The influence of the glycolide content in the polyester grafts and of the number of ester units in the grafts on thermal behavior and swellability were studied, as well as surface properties of hydrogels. Differential scanning calorimetry showed a single glass transition temperature that occurs in the range between 51 oC and 69 oC indicating the absence of phase separation.Thermogravimetry analysis of the networks showed the main loss in weight in the temperature range between 290 oC and 370 oC. The high swellability in water is characteristic of all hydrogels. Hydrophilicity, an important property of hydrogels relevant to their biomedical applications, was identified by the captive-bubble contact angle method. Hydrogels display the values of contact angle between 37 and 45 degrees which are significantly higher in comparison with the polylactide sample (57 degrees).

biodegradable hydrogels; poly(vinyl alcohol); poly(D; L-lactide); poly(D; L-lactide-co-glycolide); swellability; thermal properties; contact angle

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