Rapid, Localized, and Athermal Shape Memory Performance Triggered by Photoswitchable Glass Transition Temperature.

Abstract

Shape memory polymers that undergo shape recovery at room temperature (RT) are desirable for their potential in vivo applications, yet challenging. Herein, light-triggered athermal shape memory effect of azopolymer networks is reported by photoswitching the glass transition temperature (Tg) rather than external heating. Thanks to the switchable Tg of azopolymer induced by reversible trans-cis isomerization, the entropic energy is trapped in low Tg state (cis-form Tg < RT) to deform into a temporary shape and fixed in high Tg state (trans-form Tg > RT). Upon exposure to UV light, the reduced low Tg allows release of the entropic energy, realizing athermal shape recovery of the permanent shape. By exploring the shape memory performance, we demonstrate diverse light-induced rapid shape recovery from temporary shape to original shape. Because of the instant, precise, and spatiotemporal manipulation of light, programmable shape recovery of surface topography is further extended. We anticipate that this strategy will provide tremendous opportunities for future precise medicine devices and soft robotics.