Spatially defined crystallinity within multimaterial polymeric networks

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2023-05

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Natural systems have developed improved mechanical responses, enhancing strength and toughness by carefully including hard and soft domains. In this regard, the ability to successfully mimic these systems and create metamaterials that incorporate stiff and soft parts has remained an elusive field within polymer chemistry. Herein, methods of incorporating natural designs within engineered materials to enhance toughness and durability was explored. Simple, facile, and environmentally benign methods of delegating stiff and strong semicrystalline phases within a soft and elastic matrix using stereo-controlled ring-opening metathesis polymerization of an industrial monomer, cis-cyclooctene. Dual polymerization catalysis dictates polyolefin backbone chemistry, which enables the patterning of compositionally uniform materials with seamless stiff and elastic interfaces. Visible light–induced activation of a metathesis catalyst results in the formation of semicrystalline trans polyoctenamer rubber, out-competing the formation of cis polyoctenamer rubber, which occurs at room temperature. This bottom-up approach provides a method for manufacturing polymeric materials with promising applications in soft optoelectronics and robotics. The findings here provide a fundamental strategy to expand further the mechanisms of selective straining and flexible composite systems. With interest in spatially specified stiffness within materials, additive manufacturing was a natural progression due to the ability to develop complex 3D objects. In this regard, the monolithic nature of most resins currently employed through light-driven polymerizations limits the potential for spatial patterning within resin vat polymerizations. To this aim, a novel, majorly two-component resin formulation was developed and optimized using long alkyl chain acrylates capable of crystallizing at room temperature. The findings show the ability to tune the modulus of printed materials through modifications of the formulation with the potential to reach moduli from 176.5 ± 54.1 MPa to 0.08 ± 0.01 MPa. Lastly, dynamic covalent chemistries involving small molecule conjugate acceptors are synthesized, characterized, and have their reaction kinetics evaluated towards the aim of developing recyclable thermosets containing dynamic cross-linking.

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