Material architecture in composites fundamentally dictates material performance. In biological materials, complex architectures have long been known to impart mechanical anisotropy, toughness enhancement and fatigue resistance. Capturing the ability to design mechanical heterogeneity across multiple length scales and replicate biological patterns in engineering materials is critical to the development of lightweight, multifunctional structures with elevated strength and toughness. Dual-cure polymer networks, such as the off-stoichiometry, thiol-acrylate films discussed here, enable highly cross-linked glassy domains to be photopatterned into rubbery networks, providing an appealing material platform to capture mechanically complex structural design. Using photomasks and UV light we print glassy patterns, including a nacre-analogous microstructure, ranging in length scale from 5 µm to 1 mm, into rubbery films. Atomic force microscopy is used in conjunction with an ultramicrotome to characterize variations in material properties throughout polymeric structures with nanoscale resolution. Results show that the elastic modulus can be varied up to two orders of magnitude with excellent spatial control and exhibits a strong, continuous interface between the resulting rubber and glassy domains. Different pattern geometries are shown to impart controllable mechanical anisotropy, toughen bulk materials and guide crack propagation along complex, tortuous pathways.

Advanced composite architectures in two-stage reactive photopolymer networks

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.