Thermomechanical behaviour of biodegradable shape-memory polymer foams

Shape-memory polymer foams based on poly(omega-pentadecalactone) (PPDL) and poly(epsilon-caprolactone) (PCL) multiblock copolymer with 60 wt% PCL content were prepared by environmentally-friendly high pressure supercritical carbon dioxide (scCO(2)) foaming technique. A foam with a density of approximately 0.11 +/- 0.02 g/cm(3) and an average pore size of 150-200 mu m, with excellent compressibility and shape-memory properties was created at 25 bar/s depressurization rate in the temperature range between 78 and 84 degrees C. The shape-memory behavior of this foam was investigated using different programming modules, such as under stress-free condition and under constant strain condition. The thermally-induced shape-mernory effect (SME) was found to be strongly dependent on the programming conditions. Excellent shape fixity has been observed for all foams indicating the high efficiency of the switching domains to fix the temporary shape by crystallization. The stress recovery of this foam could be controlled by changing compression percentage (epsilon(c)%) at a constant compression temperature. The production of these foams with unprecedented properties by commercially available processing equipment raises much hope with the potential to provide new materials with a unique combination of shape-memory properties and porous structure as well as desired properties for many industrial and biomedical applications