Triblock copolymers of ε-caprolactone, L-lactide, and trimethylene carbonate: biodegradability and elastomeric...

For the triblock copolymer of ε-caprolactone, trimethylene carbonate, and L-lactide, where L-lactide blocks form the two ends, there is a range of compositions over which elastomeric behavior is obtained. Within this composition range, these polymers show good creep and recovery at ambient temperature, and exhibit high elongations to break. Additionally, we demonstrate that the recovery is independent of stress and strain for the elastomer compositions. The range of compositions that yield elastomeric character is rationalized based on the structure; specifically, there must be a minimum crystallinity of the end blocks and no crystallinity in the midblock, in addition to molar mass requirements. These polymers degrade by simple hydrolysis, and the rate of degradation is potentially programmable by manipulation of the molar ratio of hard segment to soft segment. Compared to biodegradable polyurethane, these polymers are expected to yield less harmful degradation products, and offer more variables for manipulation of properties. These polymers are also processable from the melt at temperatures exceeding about 130 °C. We expect to use these polymers in a variety of applications, including stent coatings, fully-degradable stents, and atrial septal defect occluders.