Circularly Recyclable Polymers Featuring Topochemically Weakened Carbon–Carbon Bonds

Abstract

Closed-loop circular utilization of plastics is of manifold significance, yet energy-intensive and poorly selective scission of the ubiquitous carbon–carbon (C–C) bonds in contemporary commercial polymers pose tremendous challenges to envisioned recycling and upcycling scenarios. Here, we demonstrate a topochemical approach for creating elongated C–C bonds with a bond length of 1.57∼1.63 Å between repeating units in the solid state with decreased bond dissociation energies. Elongated bonds were introduced between the repeating units of 12 distinct polymers from three classes. In all cases, the materials exhibit rapid depolymerization via breakage of the elongated bond within a desirable temperature range (140∼260 °C) while otherwise remaining remarkably stable under harsh conditions. Furthermore, the topochemically prepared polymers are processable and 3D-printable while maintaining a high depolymerization yield and tunable mechanical properties. These results suggest that the crystalline polymers synthesized from simple photochemistry and without expensive catalysts are promising for practical applications with complete materials’ circularity.

Strong and Tough Supramolecular Covalent Adaptable Networks with Room‐Temperature Closed‐Loop Recyclability

“…DOI: 10.1002/adma.202208619 offers a sustainable system for monomerpolymer-monomer circulation. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] The recovered monomers can be reused in the reproduction of the same polymers or the production of new materials with distinct properties. Furthermore, CRM could enable the removal of additives from the recycled monomers/polymers, and also the recycling of the polymers from mixed polymer wastes.…”

Multi‐Stimuli Responsive Luminescence and Domino Phase Transition of Hybrid Copper Halides with Nonlinear Optical Switching Behavior

“…Under heating, the longest Cu−I bond (2.850(2) Å) in [Cu 2 I 5 ] 3− breaks due to the weakest bond energy, forming positive and negative charge centers (Cu with positive charge, I with negative charge). Meanwhile, the Brownian motion of the molecules is enhanced, which makes it easier for reverse charge centers from two [Cu 2 I 5 ] 3− dimer to form Cu−I bonds with shorter bond length (2.773(2) Å) and making infinitely extended chains [31] . After removing the heat source, metastable β‐Gua 3 Cu 2 I 5 reversibly returns to stable α‐Gua 3 Cu 2 I 5 because of the stronger intermolecular interaction of α‐Gua 3 Cu 2 I 5 .…”

“…Meanwhile, the Brownian motion of the molecules is enhanced, which makes it easier for reverse charge centers from two [Cu 2 I 5 ] 3À dimer to form CuÀ I bonds with shorter bond length (2.773(2) Å) and making infinitely extended chains. [31] After removing the heat source, metastable β-Gua 3 Cu 2 I 5 reversibly returns to stable α-Gua 3 Cu 2 I 5 because of the stronger intermolecular interaction of α-Gua 3 Cu 2 I 5 .…”

Regiospecific Synthesis of a Reprocessable Galactan-Mimic via Topochemical Polymerization

“…Topochemical reactions, the solid-state reactions driven by the proximal arrangement of reacting groups in the crystal lattice, are attractive because of their green (solvent-free, catalyst-free) conditions, non-requirement of purification, high yield, regio-/stereospecificity, and formation of unique products that are not conceivable via solution-phase chemistry. , Topochemical reactions have paved the way not only for the synthesis of interesting small molecules − but also for the synthesis of several polymers. − However, the main bottleneck toward a successful topochemical polymerization is the pre-organization of monomers in the crystal lattice with the reactive units aligned suitably for the polymerization reaction. In order to meet such requirements, a careful molecular design is necessary.…”