Microstructure - cyclic deformation property relationships of biodegradable di-crystalline triblock copolymers

The synthesis, morphological characterization and cyclic deformation behaviour of a double crystalline triblock copolymer containing crystalline poly(l-lactide) (PLLA) or random copolymer of poly(l-lactide) and polycaprolactone (PCL) hard segment and a random copolymer of polycaprolactone and poly(trimethylene carbonate) (PTMC) soft segment are presented. The hard segment content was varied via the CL/LLA molar ratio to produce copolymer with distinct morphologies. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS) and atomic force microscopy (AFM) measurements confirmed the existence of a microphase-separated structure and the domain size was largely affected by the hard segment PCL content. Furthermore, combined measurements of WAXD and stress - strain curves revealed the molecular mechanism responsible for the superior strain recovery behaviour. It was formed that the permanent set can be largely reduced by incorporating PCL into PLLA hard segment and the strain recovery is enhanced by the ease of PCL crystal rotation upon retraction.