Shape-memory behaviors of biodegradable poly(L-lactide-co-ε- caprolactone) copolymers

A series of biodegradable poly(L-lactide-co-ε-caprolactone) (PCLA) copolymers with different chemical compositions are synthesized and characterized. The mechanical properties and shape-memory behaviors of PCLA copolymers are studied. The mechanical properties are significantly affected by the copolymer compositions. With the ε-caprolactone (ε-CL) content increasing, the tensile strength of copolymers decreases linearly and the elongation at break increases gradually. By means of adjusting the compositions, the copolymers exhibit excellent shape-memory effects with shape-recovery and shape-retention rate exceeding 95%. The effects of composition, deformation strain, and the stretching conditions on the recovery stress are also investigated systematically. A maximum recovery stress around 6.2 MPa can be obtained at stretching at T_g - 15°C to 200% deformation strain for the PCLA70 copolymer. The degradation results show that the copolymers with higher ε-CL content have faster degradation rates and shape-recovery rates, meanwhile, the recovery stress can maintain a relative high value after 30 days in vitro degradation.