Poly(caprolactone-co-oxo-crown ether)-based poly(urethane)urea for soft tissue engineering applications.

Random copolymers of epsilon-caprolactone and 2-oxo-12-crown-4 ether, poly(CL-co-OC), were used as soft segments in the synthesis of a set of poly(urethane)urea thermoplastic elastomers. With increasing OC content, the soft segment crystallinity decreased, which influenced the mechanical properties: strain induced crystallization disappeared upon the introduction of OC into poly(CL). The material therefore became weaker, however, without a reduction in strain at break. All polymers showed mechanical properties that are suitable for soft tissue engineering. Degradation studies of poly(CL-co-OC) copolymers revealed a higher intrinsic rate of hydrolysis as compared to poly(CL). When at least two neighboring OC units were present in the soft segment, a jump in the intrinsic hydrolysis rate was observed. From this study we deduced an ideal OC:CL ratio for the thermoplastic elastomer soft segments for soft tissue engineering applications. An in vitro degradation study of these poly(urethane)urea showed an increased weight loss. Combined with the enhanced hydrophilicity and reduced crystallinity, we are confident that this will indeed lead to an increased degradation rate in vivo.