Degradable networks formed from multi-functional poly(vinyl alcohol) macromers: comparison of results from a generalized bulk-degradation model for polymer networks and experimental data

Experimental and theoretical approaches were used to understand the degradation behavior of networks formed from the chain polymerization of multi-functional macromers. A typical experimental mass loss profile and theoretical model are presented and discussed to illustrate the various regions of erosion. Specifically, the degree of connectivity of the network was shown to influence the percent mass loss at reverse gelation, and the percent cyclization was shown to influence the overall shape of the mass loss profile. Finally, the theoretical predictions of mass loss were compared to experimental data for macromers with variations in their molecular weight and degree of functionality (i.e. variations in the initial network crosslinking density). Changes in the volumetric swelling ratio and compressive modulus were measured with time to obtain the degradation kinetic constant for each macromer system, ranging from 1.5 x 10(-4) min(-1) to 3.0 x 10(-5) min(-1). Results demonstrate that the theoretical predictions capture the mass loss profiles of all three systems, and as the crosslinking density of the initial network was decreased the overall time for complete degradation of the gels was also decreased. (C) 2004 Elsevier Ltd. All rights reserved.