Reconfigurable 4D Printing of Reprocessable and Mechanically Strong Polythiourethane Covalent Adaptable Networks

Abstract

4D printing has attracted tremendous interest because of its potential applications in smart devices, biomedical and tissue engineering. However, conventional shape memory polymers suffer from the single permanent shape and recovery direction, the flexibility of 4D printing is significantly limited. Besides, the cross‐linked networks of photocuring 3D‐printed objects cannot be reprocessed or repaired. To address these issues, the dynamic thiocarbamate bonds are introduced into the photocurable methacrylate to prepare reprocessable and self‐healable 4D printing polythiourethane (4DP‐PTU) with Young's modulus of 1.2 GPa and tensile strength of 61.9 MPa. The printed objects can be easily repaired by reprinting on the damaged surface. The shape memorized 4DP‐PTU features high shape fixity and shape recovery, and reconfigurable permanent shape brought by the solid‐state plasticity. A dual‐mode triggered alarm is obtained by the incorporation of carbon nanotubes to demonstrate the potential application in smart alarms for warning of laser exposure or fire case. Moreover, the surface wettability and cell adhesion performance of 4DP‐PTU with excellent biocompatibility can be facilely adjusted through the exchange reaction with sulfhydryl compounds. Accordingly, 4DP‐PTU may show vast potential applications in the field of robotics, smart alarm, bio‐implants and in solving the environmental challenges of 3D‐printed products.

Review of high-performance sustainable polymers in additive manufacturing

“…Similarly, Cui et al developed a polythiourethane-based covalent adaptable network (CAN) with a T g of 83 °C, Young's modulus of 1.2 GPa, and tensile strength of 61.9 MPa. 104 Damaged and rejoined pieces of this material, as well as hotpressed powder made from the 3D printing waste, were able to regain over 80% of the original tensile strength. Additionally, the material could be fully degraded by adding excess thiol to convert the polymer network to thiol-terminated oligomers.…”

Dynamic Covalent Hydrogels: Strong yet Dynamic

“…The polymer material is self-healing and remodeling, and the 4DP-PTU doped with carbon nanotubes enables precise localized shape control triggered by near-infrared light (NIR) for 4D printing. Meanwhile, the material has high biocompatibility and changes cell adhesion by surface modification on demand, which is of great significance for the performance of 4D printed biological implants in vivo ( Figure 8 D) [ 151 ].…”

“…Spatioselective reversible actuation in complex 3D objects [ 150 ]. Copyright © 2022 Wiley-VCH GmbH; ( D ) 4D printing polythiourethane (4DP-PTU) from dynamic thiocarbamate could be self-healing and remodeling [ 151 ]. Copyright © 2022 Wiley-VCH GmbH.…”

Dynamic covalent polymers enabled by reversible isocyanate chemistry

“…Besides the repeating actuation between two different shapes under stress-free conditions with a reversible strain of as high as 22%, the flexible transformation of complex 3D permanent shapes was achieved via solid-state plasticity controlled by dynamic thiourethane bonds without using elaborate molds. Combining 3D printing technology, Cui et al 140 prepared a thiourethane-containing methacryloyl crosslinker and mixed it with diluent methyl methacrylate (MMA) as printing precursors to fabricate 4D printed PTU CANs using the digital light processing (DLP) method (Fig. 7(b)–(d)).…”