Closed-loop chemical recycling of thermosetting polymers and their applications: a review

Healable and Recyclable Polymeric Materials with High Mechanical Robustness

To address the challenge of realizing multifunctional polymers simultaneously exhibiting high strength and high toughness through molecular engineering, ultrastrong and supertough shape‐memory poly(urea‐urethane) (PUU) is fabricated by regulating: i) the reversible cross‐links composed of rigid units and multiple hydrogen bonds, and ii) the molecular weight of soft segments. The optimal material exhibits an unparalleled strength of 84.2 MPa at a large elongation at a break of 925.6%, a superior toughness of 322.8 MJ m−3, and remarkable fatigue resistance without fracture. The repeated stretching of this material induces an irreversible deformation, which, however, can be rapidly recovered by heating. Moreover, all samples are capable of temporary shape fixation at −40 °C (recovering the original shape at 30 °C) and exhibit blue fluorescence when excited at the optimum wavelength, which is ascribed to clusterization‐triggered emission (CTE) due to the formation of microphase‐separation structures. Thus, the adopted approach provides a solution to a long‐standing problem and paves the way to the realization of intrinsically luminescent shape‐memory materials exhibiting both ultrahigh strength and ultrahigh toughness.

Molecularly Engineered Unparalleled Strength and Supertoughness of Poly(urea‐urethane) with Shape Memory and Clusterization‐Triggered Emission

Facile preparation of recyclable cyclic polyolefin/polystyrene vitrimers with low dielectric loss based on semi-interpenetrating polymer networks for high-frequency copper-clad laminates

The combination of excellent mechanical performances, high reprocess efficiency, and wide-range tunability for functional dynamic siloxane materials is a challenging subject. Herein, the fabrication of mechanically strong, autonomous self-healing, and fully recyclable silicone elastomers with unique photoluminescent properties by coordination of poly(dimethylsiloxane) (PDMS) containing coordination bonding motifs with Zn2+ ions is reported. Salicylaldimine groups, which are introduced into the polysiloxane backbone via mild Schiff-base reaction, coordinate with zinc ions to form elastomeric networks The obtained supramolecular elastomers have excellent mechanical properties, with the optimized tensile strength up to 10.0 MPa, which is unprecedented among the reported thermoplastic polysiloxane-based elastomers. Both mechanical properties and stress relaxation kinetics are tunable via adjusting the length of PDMS segments or the molar ratio of metal versus salicylaldimine. Furthermore, these elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under mild conditions. In addition, this new kind of polysiloxane also exhibits coordination-enhanced fluorescence, showing great promise for preparing photoluminescent elastomers or coatings.

Peng Xie

Papers

Solution-Processable and Thermostable Super-Strong Poly(aryl ether ketone) Supramolecular Thermosets Cross-Linked with Dynamic Boroxines