Synthesis And Characterization Of PHB Based Polyurethane Block Copolymers

Poly(ester-urethane)s (PUs) were synthesized using hexamethylene diisocyanate (HDI) or toluene diisocyanate (TDI) to join short chains (Mn 2000) of poly(R-3-hydroxybutyrate) (PHB) diols and poly(ε-caprolactone) (PCL) diols with different feed ratios under different reaction conditions. The multiblock copolymers were characterized by nuclear magnetic resonance spectrometer (NMR), fourier transform infrared (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), X-ray diffraction (XRD), contact angles measurement, scanning electron microscope (SEM) and universal testing machine. XRD spectra and second DSC heat thermograms of the multiblock copolymers revealed that the crystallization of both PHB and PCL segments was mutually restricted, especially, PCL segment limited the cold crystallization of PHB segment. SEM of platelet adhesion experiments showed the hemocompatibility was affected in some extent by the hydrophobic properties and the chain flexibility of the polymers. SEM of cell culture experiments showed the cell-compatibility was affected in some extent by cytoxicity and surface morphologies of the polymer films. Hydrolysis studies demonstrated that the hydrolytic degradation of PUs was the result of the scission of ester bonds of both PHB and PCL segments, and the rate of ester bond scission was determined in some extent by the crystallization degree, which was further affected by the configuration of polymer chains. Data from universal testing machine demonstrated that the elasticity of poly(ester-urethaned) enhanced comparing to PHB. And our study proved these multiblock poly(ester-urethanes) owed shape memory properties in some extent. These highly elastic multiblock copolymers combining hemocompatibility and biodegradability may be developed into blood contact implant materials for biomedical applications.