Solvent-assisted programming of flat polymer sheets into reconfigurable and self-healing 3D structures

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

Phase-change hybrids for thermo-responsive sensors and actuators

Highly advanced phase-change hybrids (PCHs), which consist of a phase-change material and conjugated polymer, were developed for new sensor and actuator applications. PCH films with excellent characteristics were obtained simply by depositing various molten paraffin waxes (PWs) in situ onto poly(diphenylacetylene) (PDPA) films with extremely large fractional free volumes. The phase-change enthalpy of the PWs in the hybrid films was quite high and remained constant over prolonged use. The PCH films underwent critical changes in both fluorescence (FL) intensity and color during the phase change of the PWs, which facilitated various sensor applications such as highly reversible writing/erasing, fingerprinting and array-type thermometer usage. In addition, a biaxially oriented polypropylene (BOPP)-supported PCH film exhibited extremely fast and highly reproducible thermomechanical actuation with reversible curling/uncurling during the phase change of the PWs. These findings will be useful for developing novel PCH materials with highly advanced functions and applications