BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 TABLE 2 Mechanical Properties of Some Degradable Polymers Tensile Tensile Flexural temperature Yield Polymer MPa) (%)(%) Polyglycolic acid)(MW: 50,000) 210 LPLA(MW:100,000) 2.63.3 3000 D,LPLA(Mw:107,000) 4.060 D, L-PLA(MW: 550,000 y(B-hydroxybutyrate)(MW: 422,000) oly(e-caprolactone)(MW: 44,000) 7.080 polyanhydrides SA-HDA anhydride)(MW: 142,000) Poly(ortho esters) DETOSU: t-CDM: 1, 6-HD (MW: 4.1220 Poly(BPa PA imidocarbonate)(MW 2150 TH iminocarbonate)(MW: 103, 000) 55 B, ..A100: 35: 65 copolymer of 3. 9-bistethylidene 2, 4.8, 10-tetraoxaspirol5, undecane)(DETOSU), trans-cyclohexane dimethanol (t-CDM)and hexanediol(1, 6-HD) was selected as a specific example. "BPA: Bisphenol A; DTH: desaminotyrosyl-tyrosine hexyl ester. For detailed structures, see Fig. 1 tner, Biomaterials Science)*Semicrystalline materials highlighted Physical chemistry of hydrolysis Mechanisms of dissolution two modes of erosion surface and bulk surface erosion -degradation from exterior only with little/no water penetration into bulk bulk erosion- water penetrates entire structure and degrades entire device simultaneously surface erosion bulk-erosion Fig. I. Schematic illustration of the changes a polymer matrix undergoes during surface erosion and bulk erosion. Lecture 1-IntroductionBEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 1 – Introduction (Ratner, Biomaterials Science) *Semicrystalline materials highlighted Physical chemistry of hydrolysis Mechanisms of Dissolution • two modes of erosion: surface and bulk surface erosion – degradation from exterior only with little/no water penetration into bulk bulk erosion – water penetrates entire structure and degrades entire device simultaneously