Abstract
It is extremely challenging, yet critically desirable to convert 2D plastic films into 3D structures without any assisting equipment. Taking the advantage of solvent-induced bond-exchange reaction and elastic-plastic transition, shape programming of flat vitrimer polymer sheets offers a new way to obtain 3D structures or topologies, which are hard for traditional molding to achieve. Here we show that such programming can be achieved with a pipette, a hair dryer, and a bottle of solvent. The polymer used here is very similar to the commercial epoxy, except that a small percentage of a specific catalyst is involved to facilitate the bond-exchange reaction. The programmed 3D structures can later be erased, reprogrammed, welded with others, and healed again and again, using the same solvent-assisted technique. The 3D structures can also be recycled by hot-pressing into new sheets, which can still be repeatedly programmed.
Highlights
It is extremely challenging, yet critically desirable to convert 2D plastic films into 3D structures without any assisting equipment
The shape programming is achieved by the following generic procedure: [1] the flat sheet of the vitrimer is heated to 45 °C and stretched, it is cooled down to below Tg to freeze this pre-strained shape; [2] the solvent is selectively deposited onto the desired area of the free-standing pre-strained film, and allowed to evaporate naturally; [3] the sample is reheated to above Tg, at which time the new natural 3D shape is adopted
We explain the mechanism of solvent-induced plastic deformation
Summary
It is extremely challenging, yet critically desirable to convert 2D plastic films into 3D structures without any assisting equipment. Shape programming is normally based on the self-folding or bending of active materials, giving rise to the designed new shapes in response to an external stimulus without the external force[5,6], which is necessary for the traditional processing of plastics This offers a promising strategy to access 3D structures which cannot be obtained by traditional methods[4]. No matter what kind of material it is, very few 3D structures obtained from folding a 2D film are capable of reprogramming and reshaping, nor are they weldable or capable of self-healing Such abilities would greatly extend the service lifetime and expand service areas[32,33].
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