Shape memory polyurethanes (SMPUs) remain one of the main classes of SMPs studied. Their
attractiveness mainly lies in their ease of processing and low cost. Ratna & Karger-Kocsis (6)
recently reviewed current advances in terms of the chemical structure/composition of SMPUs.
These researchers found that optimized SM effects were obtained at a hard-segment content
of 35 to 40 wt% for glassy thermoplastic SMPUs and at a soft-segment molecular weight
of 5000–6000 g mol−1 for semicrystalline SMPUs. In addition, the importance of molecular
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design was highlighted. The authors reported that the incorporation of rigid aromatic structures
and/or of more planar molecules supported higher SM performances owing to stronger molecular
interactions.