This work was focused on compounding and fabrication of two-way shape memory materials. Two-way shape memory (i.e. actuation) is possible by incorporating a phase change material (PCM) into an elastomer, where the volumetric change of the PCM undergoing a phase transition dilates the elastomer. Here formulations were investigated using, polystyrene-block-poly(ethylene-co-butylene)-block polystyrene (SEBS), a thermoplastic elastomer; linear alkanes as the phase change additive, and polyphenyl ether (PPE). The inclusion of PPE was driven by two goals, first, retain the anisotropic cylinder morphology of the initial SEBS after blending with the ethylene-butylene (EB)-selective alkane, and second to gain a large separation between the melting point of the alkane and the glass transition temperature of the polystyrene (S) domains. As PPE is selective to the S domains, it can both counterbalance the selective swelling of the EB domains and increase the T<sub>g</sub> of the S domains. The structure-property relationships of these formulations will be presented. In addition, efforts to 3D print these materials by extrusion-based methods to obtain materials with anisotropic properties will be discussed.

Compounding of two-way shape memory polymers

ACS Spring 2022

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