Synthesis of biodegradable poly(propylene fumarate) networks with poly(propylene fumarate)-diacrylate macromers as crosslinking agents and characterization of their degradation products

New biodegradable poly(propylene fumarate)-based polymer networks have been prepared by radical polymerization using poly(propylene fumarate) (PPF) an d poly(propylene fumarate)-diacrylate (PPF-DA) macromers. Two PPF-DAs were synthesized incorporating one (rn = 1) and two (m = 2) fumarate units, and were employed in the synthesis of the polymer networks. The PPF/PFF-DA doub le bond ratio and the molecular weight of PPF-DA were varied to assess thei r effects on the mechanical properties of the resulting polymer networks as well as on their equilibrium water content. The compressive strength at fr acture of PPF/PPF-DA (m = 1) polymer networks increased from 11.2 +/- 1.8 t o 66.2 +/- 5.5 MPa as the double bond ratio of PPF/PPF-DA (rn = 1) decrease d from 4 to 0.5, An increase in compressive modulus was also observed from 19.4 +/- 1.8 to 340.2 +/- 30.7 MPa for the same range of the double bond ra tio of PPF/PPF-DA. Increasing the molecular weight of PPF-DA (rn = 2) cause d both the compressive strength at fracture and modulus of the correspondin g polymer networks to increase to the ranges of 14.4 +/- 4.2 to 88.2 +/- 6. 1 MPa and 28.0 +/- 2.4 to 480.4 +/- 35.9 MPa, respectively. Similarly, both were increased as the PPF/PPF-DA (m = 2) double bond ratio decreased from 4 to 0.5. The PPF/PPF-DA crosslinked polymer networks showed negligible equ ilibrium water content for all 10 formulations tested in this study. The de gradation reaction of the PPF/PPF-DA polymer networks under basic condition s was investigated. The degradation products were isolated and characterize d by NMR and GC/MS as fumaric acid, propylene glycol, and poly(acrylic acid -co-fumaric acid) of weight average molecular weight of 5080. These data de monstrate that biodegradable PPF/PPF-DA polymer networks should have great potential as polymer scaffolds for orthopedic applications in tissue engine ering. (C) 2000 Published by Elsevier Science Ltd.