Fundamental studies of a novel, biodegradable PEG-b-PLA hydrogel

The degradation behavior of highly swollen, chemically cross-linked hydrogels was characterized by monitoring changes in their mass loss, degree of swelling and compressive modulus. The hydrogels were used as model systems to investigate the hydrolytic degradation process in cross-linked networks. The trends of the three measured properties differ substantially from those seen for Linear degradable systems; however, they can still be predicted accurately using hydrolysis kinetics and network structure. Experimental results show that the modulus decreases exponentially with time while the volumetric swelling ratios for these gels increase exponentially. The characteristic exponential time constants for these two functions, as well as the overall degradation timescale, are influenced greatly by the network structure. Thermodynamic relationships are used to explain these trends as well as relating the observed tradeoff between the two desirable properties of mechanical strength and water content. (C) 2000 Elsevier Science Ltd. All rights reserved.