Toughening CO 2 -derived copolymer elastomers through ionomer networking Kam Poon, Georgina L. Gregory, Gregory S. Sulley, Fernando Vidal,
Charlotte K. Williams University of Oxford, UK
Utilizing carbon dioxide (CO 2 ) to make polycarbonates through the ring-opening copolymerization (ROCOP) of CO 2 and epoxides valorizes and recycles CO 2 and reduces pollution in polymer manufacturing. 1, 2 Recent developments in catalysis provide access to polycarbonates with well-defined structures and allow for copolymerization with biomass-derived monomers; however, the resulting materials thermal-mechanical properties are under-investigated. 3, 4 Here, new CO 2 -derived thermoplastic elastomers (TPE) are described together with a generally applicable method to augment tensile mechanical strength and Young’s modulus without requiring material re-design are described. 5 The block thermoplastic elastomers combine high glass transition temperature ( T g ) amorphous blocks comprising CO 2 -derived poly(carbonates) (A-block), with low T g poly(ε-decalactone), from castor oil, (B-block) in ABA structures. The poly(carbonate) blocks are selectively functionalized with metal-carboxylates, where the metals are Na(I), Mg(II), Ca(II), Zn(II) and Al(III). The colorless polymers, featuring <1 wt% metal, show tunable thermal ( T g ), and mechanical (elongation at break, elasticity, creep-resistance) properties. The best elastomers show >50-fold higher Young’s modulus and 21-fold greater tensile strength, without compromise to elastic recovery, compared with the starting block polymers. They have wide operating temperatures (-20 to 200 ˚C), high creep-resistance and yet, by balancing metal loading, remain recyclable. Overall, well-controlled polymerizations of carbon dioxide and co-monomers produce block polymers elastomers whose properties are straightforward to modify according to application need. In future, these materials could substitute high-volume petrochemical TPEs, e.g. styrenic or acrylic block polymers, and be ultilized in high-growth fields like medicine, robotics and electronics. References 1. Hepburn, C.; Adlen, E.; Beddington, J.; Carter, E. A.; Fuss, S.; Mac Dowell, N.; Minx, J. C.; Smith, P.; Williams, C. K. The technological and economic prospects for CO2 utilization and removal. Nature 2019 , 575 (7781), 87-97. DOI: 10.1038/ s41586-019-1681-6. 2. von der Assen, N.; Jung, J.; Bardow, A. Life-cycle assessment of carbon dioxide capture and utilization: avoiding the pitfalls. Energy & Environmental Science 2013 , 6 (9), 2721-2734. DOI: 10.1039/c3ee41151f. 3. Sulley, G. S.; Gregory, G. L.; Chen, T. T. D.; Carrodeguas, L. P.; Trott, G.; Santmarti, A.; Lee, K. Y.; Terrill, N. J.; Williams, C. K. Switchable Catalysis Improves the Properties of CO2-Derived Polymers: Poly(cyclohexene carbonate-b-epsilon- decalactone-b-cyclohexene carbonate) Adhesives, Elastomers, and Toughened Plastics. J. Am. Chem. Soc 2020 , 142 (9), 4367-4378. DOI: 10.1021/jacs.9b13106. 4. Gregory, G. L.; Sulley, G. S.; Kimpel, J.; Lagodzinska, M.; Hafele, L.; Carrodeguas, L. P.; Williams, C. K. Block Poly(carbonate-ester) Ionomers as High-Performance and Recyclable Thermoplastic Elastomers. Angew. Chem., Int. Ed. 2022 , 61 (47). DOI: 10.1002/anie.202210748. 5. Poon, K. C.; Gregory, G. L.; Sulley, G. S.; Vidal, F.; Williams, C. K. Toughening CO2 -Derived Copolymer Elastomers Through Ionomer Networking. Adv. Mater. 2023 , e2302825. DOI: 10.1002/adma.202302825.
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