Controlling the switching temperature of biodegradable shape memory polymers composed of stereocomplex polylactide / poly(_D,L-lactide-co-ε-caprolactone) blends

We synthesized new biodegradable shape-memory polymers (SMPs) by blending synthesized poly(_D,L-lactide-co-ε-caprolactone) (PLCL) and stereocomplex polylactide (sc-PLA) to be used as biomaterials for medical devices. PLCL copolymers (M_n ∼80,000) with various monomer ratios (LA:CL) were synthesized by the bulk ring-opening polymerization. The glass transition temperature of the resulting PLCL copolymers could be well controlled from −3 °C to 60 °C, agreeing well with the values by the Gordon-Taylor equation, confirming the homogeneous random distribution of LA and CL monomers in the synthesized PLCL. The synthesized PLCL and sc-PLA were eventually blended for the fabrication of biodegradable SMPS. The PLCL/sc-PLA blend samples possessed the sc-PLA crystallinity of ∼13%, which effectively worked as crosslinkings, exhibiting shape-memory behavior with various switching temperatures (30.5°C–62 °C) and shape-recovery ratios realized by adjusting the CL ratio of the PLCL copolymers: a lower CL ratio resulted in a higher switching temperature and a higher shape-recovery ratio.