Poly(ε-caprolactone) and Pluronic Diol-Containing Segmented Polyurethanes for Shape Memory Performance

A series of novel segmented linear and crosslinked polyurethanes (PUs) are synthesized from poly(epsilon-caprolactone) (PCL) (25 kg mol(-1)), methylene diphenyl diisocyanate (MDI), and various polyether diols (Pluronic (PLU) and polyethylene glycol (PEG)). The basic structures of the highly deformable PUs are PLU/PEG-MDI-PCL-MDI-PLU/PEG and PLU-MDI-PCL-MDI-PLU, respectively. The linear and crosslinked PUs are characterized. Changes in the tensile behavior are attributed to the effects of compositional variables and alterations in the crosslink density. Additional information on the morphology of the segmented PUs is deduced from differential scanning calorimetry, as well as transmission and scanning electron microscopy investigations. Both the linear and the crosslinked PUs exhibit a broad rubbery plateau above the melting temperature of the crystalline PCL phase, which is highly beneficial for shape memory function. This work highlights that the chemical build-up of soft segments containing high-molecular-weight crystallizable chain units is a proper tool to tailor the morphology and mechanical properties of PUs, and thus also their shape memory properties.