Journal Article

Shape-memory effects in molecular crystals

Naumov, Panče, Warren, Mark, Karothu, Durga Prasad, Ahmed, Ejaz

2019

Overview

Molecular crystals can be bent elastically by expansion or plastically by delamination into slabs that glide along slip planes. Here we report that upon bending, terephthalic acid crystals can undergo a mechanically induced phase transition without delamination and their overall crystal integrity is retained. Such plastically bent crystals act as bimorphs and their phase uniformity can be recovered thermally by taking the crystal over the phase transition temperature. This recovers the original straight shape and the crystal can be bent by a reverse thermal treatment, resulting in shape memory effects akin of those observed with some metal alloys and polymers. We anticipate that similar memory and restorative effects are common for other molecular crystals having metastable polymorphs. The results demonstrate the advantage of using intermolecular interactions to accomplish mechanically adaptive properties with organic solids that bridge the gap between mesophasic and inorganic materials in the materials property space. Molecular crystals can be bent elastically by expansion or contraction on opposite faces, or plastically by delamination into slabs that glide along slip planes. Here the authors report crystals that can be bent plastically while undergoing a mechanically induced phase transition without delamination.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 147/135 / 639/301/1023/303 / 639/301/923/3931 / 639/638/298/303 / Bimorphs / Crystals / Delamination / Heat treatment / Humanities and Social Sciences / Inorganic materials / Material properties / multidisciplinary / Organic solids / Phase transitions / Polymers / Science / Science (multidisciplinary) / Shape effects / Shape memory alloys / Slip planes / Terephthalic acid / Transition temperature / Transition temperatures