Triple one-way and two-way shape memory poly(ethylene-co-vinyl acetate)/poly(ε-caprolactone) immiscible blends

Triple one-way and two-way shape memory polymers (1W-SMPs and 2W-SMPs) are highly desirable for many practical applications due to the multiple shape transformation. In this work, the blend with co-continuous structure is fabricated based on poly(ethylene-co-vinyl acetate) (EVA) and poly(epsilon-caprolactone) (PCL), which shows excellent triple one-way and two-way shape memory properties. It is found that the blends have two independent crystallization peaks and two independent melting peaks. With the increase of dicumyl peroxide (DCP) content, the crystallization temperature, melting temperature, and crystallinity of both EVA and PCL in the blends gradually decreases. The blends show great dual and triple one-way shape memory property, and the phenomena of elongation induced by oriented crystallization and contraction induced by melting are clearly seen. Moreover, the blends exhibit remarkable and recyclable triple two-way shape memory performance, with an average shape recovery magnitude of 97.3% and an average actuation magnitude of 50.6%. In terms of the excellent triple one-way and two-way shape memory performance, the EVA/PCL blends may have potential applications in the fields of soft robotics, actuators, and cranes. The new preparation method of triple 2W-SMPs can be used to fabricate other triple 2W-SMPs with commercial polymers.

Automated summary

The study presents a new method for fabricating triple one-way and two-way shape memory polymers using blends of EVA and PCL. The blends show excellent shape memory properties with dual and triple one-way shape memory capabilities, as well as remarkable and recyclable triple two-way shape memory performance. This new preparation method may have potential applications in soft robotics, actuators, and cranes.