PPDO/PCL/PEG based amphiphilic polyurethanes with controllable degradation and mechanical retention

Abstract

Polyester-based biodegradable polymers are widely used in absorbable medical devices; however, the hydrophobic nature of polyesters limits their application in implantation under conditions requiring rapid degradation. This work reports poly(p-dioxanone) (PPDO) based short-term degradable polyurethanes with controllable degradation and mechanical properties. Three polyurethanes composed of poly(ε-caprolactone) (PCL), a poly(p-dioxanone)–poly(ethylene glycol)–poly(p-dioxanone) (PPDO–PEG–PPDO) triblock copolymer and polyethylene glycol (PEG) were synthesized with hexamethylene diisocyanate (HDI) as the chain-extender. The resulting polyurethanes exhibited a desirable balance of tensile strength (>20 MPa) and exceptional extensibility (elongation at break >1100%) as well as tunable stiffness (Young's modulus, 12–54 MPa). In artificial urine, the copolymers (PDEUs) exhibited composition-dependent mechanical degradation. The mechanical performance decreased in a near-linear time-dependent manner and the mechanical persistence times were 12, 34, and 52 days for PDEU_1.5, PDEU_3.5, and PDEU_5.5, respectively. The structural analyses showed that the degradation was dominated by PPDO chain scission and depletion of a PPDO-rich amorphous phase, whereas PCL crystallinity provided structural stabilization. Additionally, PEG was largely retained to maintain the hydrophilicity of the degradation products. Overall, the degradation kinetics and mechanical lifetime of PDEUs could be tailored by adjusting PPDO/PCL compositions for providing hydrophilic copolymers with rapid and controllable degradation in biomedical applications.