Triple-Shape Effect with Adjustable Switching Temperatures in Crosslinked Poly[ethylene-co-(vinyl acetate)]


A triple-shape capability of copolymer networks enabling a variation of the two switching temperatures Tsws by purely physical functionalization is introduced. The polymer networks obtained by covalently crosslinking of poly[ethylene-co-(vinyl acetate)] exhibit a broad melting transition. The influence of the two deformation temperatures Tdeforms applied during programming of the triple-shape effect (TSE) on the two Tsws is explored. Interestingly, it turns out that the deformation geometry plays an important role in the realizability of this concept. Tensile deformations allow adjusting only one Tsw in the lower melting temperature range of 45 to 60 °C, whereas in bending tests, both Tsws can be varied. Finally, two independent TSEs associated to four different Tsws between 45 and 90 °C can be realized in the same specimen. Shape fixity and shape recovery ratios generally exceed 90%, demonstrating an excellent performance of the triple-shape function.
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