Segmental composition-dependent enzymatic degradation of poly(ε-caprolactone)-based polyurethanes and poly(urethane-amide)s

Poly(ε-caprolactone) (PCL)-based polymers are biodegradable materials that have been widely used in biomedical applications. However, their inherently slow hydrolytic degradation and limited controllability restrict applications that require defined degradation lifetimes. Herein, tunable degradability is demonstrated in a series of segmented polymers, including PCL-based polyurethanes (PCL-PU) and poly(urethane-amide)s (PCL-PUA), using a lipase-catalyzed degradation model. These polymers were synthesized via the hexamethylene diisocyanate (HDI)-mediated polyaddition of PCL diols with different number-averaged molecular weights (M n 530, 2000, and 4000 g/mol) as soft segments, two diamide-diol chain extenders with distinct rigidities (aliphatic versus aromatic), and HDI as hard segments. The corresponding PCL-PUs prepared from PCL diol and HDI were used as controls. Systematic enzymatic degradation studies were conducted to investigate the effects of soft-segment length and hard-segment composition on degradation behavior. The degradation process was comprehensively analyzed by monitoring the mass retention, morphology, chemical structure, molecular weight, thermal properties, crystalline structure, microphase-separated behavior, and surface hydrophilicity of the degraded films. The results revealed clear relationships between segmental composition and enzymatic degradability. This work establishes a structure and degradability relationship in PCL-based segmented polymers and provides fundamental insights for designing degradable materials with tunable degradation lifetimes.