Water-blown polyurethane (PU) foams are of enormous technological interest as
they are widely applied in various fields, i.e., consumer goods, medicine,
automotive or aerospace industries. The discovery of the one-way shape-memory
effect in PU foams provided a fresh impetus for extensive investigations on
porous polymeric actuators over the past decades. High expansion ratios during
the shape-recovery are of special interest when big volume changes are
required, for example to fill an aneurysm during micro-invasive surgery or
save space during transportation. However, the need to program the foams
before each operation cycle could be a drawback impeding the entry of shape-
memory polymeric (SMP) foams to our daily life. Here, we showed that a
reversible shape-memory effect (rSME) is achievable for polyurethane water-
blown semicrystalline foams. We selected commercially available crystallizable
poly(ε-caprolactone)-diols of different molecular weight for foams synthesis,
followed by investigations of morphology, thermal, thermomechanical and shape-
memory properties of obtained compositions. Densities of synthesized foams
varied from 110 to 180 kg∙m−3, while peak melting temperatures were
composition-dependent and changed from 36 to 47 °C, while the melting
temperature interval was around 15 K. All semicrystalline foams exhibited
excellent one-way SME with shape-fixity ratios slightly above 100% and shape-
recovery ratios from the second cycle of 99%. The composition with broad
distribution of molecular weights of poly(ε-caprolactone)-diols exhibited an
rSME of about 12% upon cyclic heating and cooling from Tlow = 10 °C and Thigh
= 47 °C. We anticipate that our experimental study opens a field of systematic
investigation of rSMEs in porous polymeric materials on macro and micro scale
and extend the application of water-blown polyurethane foams to, e.g.,
protective covers with zero thermal expansion or even cushions adjustable to a
certain body shape. View Full-Tex