Synthesis And Characterization Of Biodegradable Polyurethanes With Unsaturated Carbon Bonds Based On Poly(Propylene Fumarate)

Segmented polyurethanes (SPUs) synthesized from biodegradable polyesters are very promising due to their excellent biodegradability, biocompatibility and physical properties. They offer tremendous potentials in many applications such as drug delivery, tissue engineering and regenerative medicine etc. So far most SPUs have been derived from the saturated macromolecular polyols such as PCL (Poly(ε-caprolactone)), PC (Polycarbonate), and PHB (Poly-β-hydroxybutyrate), and are lack of enough reactive sites to be modified and functionalized. Poly(propylene fumarate) (PPF) is a linear aliphatic unsaturated polyester which has been extensively investigated in biomedical applications. Synthesis of polyurethanes (PPFUs) based on the PPF-diol could provide a new kind of biomaterials for application.In this work, the monomer of PPF was synthesized by reaction between fumaric acid and propylene oxide, which was then synthesized to PPF by a self-transesterification reaction. The obtained PPF was strictly hydroxyl ended and the exact hydroxyl value was titrated according to ISO 2554-1974.Then PPFUs were synthesized by a two-step reaction using dibutyltin dilaurate as catalyst in anhydrous 1,4-dioxane. By varying the diisocyanates, chain extender and hard segment contents, the obtained PPFUs had different chemical compositions. The relationship between structure and properties was investigated by FITR, GPC, DSC, XRD and TEM. In vitro degradation and cell culture experiments illustrated the excellent diodegradablity and biocompatibility of PPFUs. It indicates that the properties of PPFUs could be varied and easily controlled by changing the composition.Finally, PPFU was functionalized with chiral oligomers (L,D-PAV). The chiral monomers are obtained by reaction between valine and acryloyl chloride, and then synthesized to chiral oligomer by reversible addition-fragmentation chain transfer polymerization (RAFT). The oligomers are hydrolyzed to obtain sulfhydryl end groups and then covalently immobilized to PPFU via Michael addition. The influence of the functionalized surface to stem cells growth was investigated.