Leveraging polymer architecture to build multi-materials with extreme stiffness contrast

Biology is replete with examples of strong and tough multi-materials (e.g., nacre, bones) with diverse functions. The robustness of these materials is attributed to their precise hierarchical structure and stiffness mismatch. Over the years, synthetic polymers and composites, owing to their versatility, have garnered interest as mimics for these natural systems. This presentation will discuss the design and 3D printing of polymeric multi-materials with spatially controlled stiffness via digital light processing.

Photoinitiation and curing of two independent polymer networks – bottlebrush elastomers and epoxy linear networks – will be shown to result in super-soft (<100 kPa) and stiff (~1 GPa) domains, respectively. Specifically, this presentation will discuss the influence of bottlebrush architecture on the mechanical performance of the super-soft domains, as well as the interfacial properties of the soft-stiff domains. The orthogonal wavelength response and polymerization mechanisms resulting in excellent spatiotemporal stiffness control during layerwise 3D printing will be discussed. The choice of the photochemical components will be shown to influence the curing kinetics, the printing parameters, and mechanical performance of the 3D printed multi-materials. Finally, the toughness, tensile strength, and elastic moduli of these multi-materials will be discussed in the context of biologically relevant hierarchical systems.