(560c) Macro to Micro: Emulating Natural Toughening Mechanisms in Multimorphic Soft Materials Via Orthogonal Interpenetrating Polymer Networks

Natural materials exhibit enhanced toughness and resilience through the use of controlled patterning of soft and hard materials. Efforts to emulate such materials are synthetically challenging due to difficulties in adhesion between dissimilar materials, and the ability to effectively pattern on the length scale required to induce toughening mechanisms. To this end we present a simple, light based, one-pot method to synthesize interpenetrating polymer networks. Two chemically distinct monomers are mixed into a single resin, and polymerized orthogonally using individual stimuli, giving control over each network formation. Varying the time between initiations gives control over the resulting morphology and mechanical properties. Characterization of networks formed with different time delays, using atomic force microscopy, shows dramatic differences in network mixing which are accompanied by large differences in tensile properties and fracture toughness. These differences are leveraged for spatial control over mechanical properties in a single sample using photopatterning. Patterned materials show strong adhesion between hard and soft regions due to chemical homogeneity between the domains, and continuous networks throughout. The ability to produce hierarchical structures, composed of a single, multimorphic polymer system is demonstrated, providing a tool for the production of bio-inspired structures.