Supramolecular polymer networks shape memory

Abstract This chapter introduces the moisture-induced shape memory effect (SME) observed in supramolecular shape memory polymers, particularly shape memory polyurethane (SMPU), containing pyridine moieties. The moisture absorption of polyurethane networks containing pyridine moeties (PUPy) is discussed followed by an investigation into the effect of relative humidity (RH), temperature, BINA content and MDI-BDO content. The induence of moisture absorption on both the thermal properties and the dynamic mechanical properties of SMPUs is also described, along with the moisture-induced SME mechanism. 

Figure 3.1 Various molecular structures of shape memory polymers (SMPs). A stable network and a reversible switching transition are the prerequisites for the polymers to show the shape memory effect (SME). The stable network can be molecule entanglement, chemical cross-hnking, crystaUization, and IPN the reversible switching transition can be the crystalUzation/melting transition, vitrification/glass transition, anisotropic/isotropic transition, reversible chemical cross-linking, and association/disassociation of supramolecular structures. Source [22] Reproduced with permission from Elsevier...

FIGURE 5.2.3 Classification of soft shape-memory materials from the viewpoint of nanoaivhitectonics. (a-c) Structures and (d) molecular mechanism, (a) Chemically cross-linked polymer network, (b) supramolecular network with clay nanosheets [29], and (c) inorganic/polymer composite network system, and their shape-memory profiles [30]. (d) The nanoscale molecular mechanism for one-way and two-way SME of a cross-linked semicrystalline polymer system. 

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