A stretchable electronic skin (e-skin) requires a durable elastomeric matrix to serve in various conditions. Therefore, excellent and balanced properties such as elasticity, water proof capability, toughness, and self-healing are demanded. However, it is very difficult and often contradictory to optimize them at one time. Here, a polyurethane (BS-PU-3) containing a polydisperse hard segment, hydrophobic soft segment, and a dynamic disulfide bond was prepared by one-pot synthesis. Unlike the normal two-pot reaction, BS-PU-3 obtained through the one-pot method owned a higher density of self-healing points along the main chain and a faster self-healing speed, which reached 1.11 μm/min in a cut-through sample and recovered more than 93% of virgin mechanical properties in 6 h at room temperature. Moreover, a remarkable toughness of 27.5 MJ/m3 assures its durability as an e-skin matrix. Even with a 1 mm notch (half of the total width) on a standard dumbbell specimen, it could still bear the tensile strain up to 324% without any crack propagation. With polybutadiene as the soft segment, the shape, microstructure, and conductivity in BS-PU-3 and BS-PU-3-based stretchable electronics kept very stable after soaking in water for 3 days, proving the super waterproof property. An e-skin demo was constructed, and self-healing in pressure sensitivity, mechanical, and electrical properties were verified.

A series of biobased poly(butylene carbonate-cofurandicarboxylate) (PBCF), are synthesized through a twostep polycondensation reaction. Chemical structures, thermal properties, crystallization behaviors, mechanical properties, barrier properties, and enzymatic degradation of PBCFs are investigated. The linear variation of the glass transition temperatures with the content ratio confirms the good miscibility between butylene carbonate (BC) and butylene furandicarboxylate (BF) units. BF segments could crystallize in most contents under different temperatures. Consequently, mechanical properties of these copolymers depend not only on the composition but also on the annealing conditions. Longtime annealing at room temperature or short-time annealing under high temperature could tremendously increase the tensile modulus. For room-temperature annealing, the formation of less perfect crystals of the poly(butylene furandicarboxylate) (PBF) could interpret the enhancement of modulus. On the other hand, the high-temperature annealing induces more perfect PBF crystals and improves the modulus significantly too. The tensile toughness of the PBCFs is good with the lowest elongation at break of 260%, and the degradation could be observed in samples with less than 60 mol % BF units. With good gas barrier properties, fast biodegradability, and high mechanical performance, these copolyesters possess potential applications in the plastic industry.

No abstract