Triple-shape memory polymers

A triple-shape memory polymer containing a UPy unit (Ware efa/., 2012). 

Ware, X, Hearon, K., Lonnecker, A., Wooley, K. L., Maitland, D. J., Voit, W. (2012), Triple-shape memory polymers based on self-complementary hydrogen bonding. Macromolecules, 45(2), 1062-9. 

Triple SMPs have one permanent shape and two temporary shapes, compared to the traditional double shape memory polymers (SMPs) that have only one permanent and one temporary shape. Triple SMPs can therefore provide more complex actuation than double SMPs. While double SMPs only need one reversible phase, triple SMPs generally need two reversible phases. Zhao et al. [13] first built a co-continuous architecture in immiscible polyethylene (PE)/polypropylene (PP) blends, and then prepared triple SMPs through chemical crosslinking of the blends. The co-continuous window of typical immiscible PE/PP blends is a volume fraction of PE of approximately 30-70 vol.%. This architecture can be stabilized by chemical crosslinking. Different initiators, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane (DHBP), dicumylperoxide (DCP) coupled with divinylbenzene (DVB) (DCP-DVB), and their... 

Xie, T., Xiao, X., and Cheng, Y.T. (2009) Revealing triple-shape memory effect by polymer bilayers. Macro-molecular Rapid Communications, 30, 1823 1827. 

Li, J. and Xie, T. (2011) Significant impact of thermo-mechanical conditions on polymer triple-shape memory effect. Macromolecules, 44, 175-180. 

Shape memory polymers (SMPs) and composites thereof are emerging smart materials in different applications, especially in biomedical, aerospace, and construction engineering helds. SMPs may adopt one (dual-shape), two (triple-shape). 

Triple-shape polymers can change on demand from a first shape (A) to a second shape (B) and from there to a third shape (C), when stimulated by two subsequent temperature increases [10, 26, 27]. Specific cyclic, thermomechanical tensile experiments were developed to characterize the triple-shape effect (Chapter Shape-Memory Polymers and Shape-Changing Polymers [101] and Sect. 2.2) quantitatively. Analogous to the experiments for dual-shape materials, each cycle of these tests consisted of a programming and a recovery module. A cycle started with creating the two temporary shapes (B and A) by a two-step uniaxial deformation, followed by the recovery module, where shape (B) and finally shape (C) were recovered. 

Kumar, U.N., Kratz, K., Behl, M., and Lendlein, A. (2012) Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments. eXPRESS Polym. 

A detailed understanding of the underlying mechanisms for the SME requires a systematic characterization, especially quantification of the shape-memory properties. As typical for a material function, numerous physical parameters are in-fiuencing the SME. Therefore the determination of structure/physical parameter function relationships is challenging. Specific methods are required for dual-shape or triple-shape properties as well as for the different stimuli. The knowledge-based development of SMPs can be supported by modeling approaches for simulating the thermomechanical behavior of such polymers. 

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