Polymer Networks with Shape Memory Effect

Polymer Networks with Shape Memory Effect... 

There are several excellent reviews on the SMP [15-20]. The present review focuses on the SMP synthesized from polymer blending technique. Polymer blending is an effective and economical way to develop the new polymeric materials with desirable properties. Numerous polymer blends exhibiting shape memory effects have been reported, which can be classified into miscible blend, immiscible blend, interpenetrating polymer network (IPN), and cross-linked blends. 

FIGURE 19.4 Molecular mechanism and macroscopic effect of a shape-memory polymer, (a) Schematic representation of the thermally induced shape-memory effect of a polymer network with (b) Shape recovery of a stent with T = 52° in water at 37°C. The stent gradually changed from its... 

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...

Li, )., Liu, T, Pan, Y., Xia, S., Zheng, Z., Ding, X., and Peng, Y. (2012) A versatile polymer co-network with broadened glass transition showing adjustable multiple-shape memory effect Macromol. Chem. Phys., 213 (21), 2246-2252. 

Structural concepts for tissue-compatible and biodegradable polymers, thermoplastic elastomers, and thermosets with shape memory capabilities will be introduced. Their thermal and mechanical properties and degradation behaviour will be explained. An important precondition for the shape memory effect of polymers is elasticity. An elastic polymeric material consists of flexible segments, so-called network chains, which are connected via netpoints or junctions. The permanent shape of such a polymer is determined by the netpoints. The network chains take a coil-like conformation in unloaded condition. If the polymer is stretched, the network chains become extended... 

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. 

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