Rapid Manufacturing of Elastomers, Thermosets and Composites with Tunable Multifunctional Properties

Complex patterns and gradients integral to the structure and function of biological materials emerge spontaneously through reaction-diffusion controlled processes during morphogenesis. In contrast, functional patterns in synthetic materials are created through multistep manufacturing processes requiring masks, molds, or printers. Current additive manufacturing techniques for fabricating complex, architected materials often face limitations in achieving the desired level of complexity and control without extensive human intervention and additional tools. Inspired by reaction-diffusion systems in nature, our work seeks to harnesses rapid reaction-thermal transport during frontal polymerization to drive the emergence of spatially varying patterns and tailor properties of polymers and composites during the manufacturing. Tuning of the reaction kinetics and thermal transport enables internal feedback control over thermal gradients to spontaneously pattern morphological, chemical, optical, and mechanical properties of structural materials. A range of experimental tools are exploited to characterize the evolution of the microstructure and properties, including IR imaging of the temperature history and front evolution, differential scanning calorimetry to determine degree of cure, wide angle x-ray scattering, nanoindentation and mechanical testing to assess changes in thermomechanical properties. Functionally graded and patterned regions with two orders of magnitude change in modulus and over 200°C change in glass transition temperature are achieved in thermoset polymers. Small perturbations in the fabrication conditions lead to remarkable changes in the strength, elastic modulus, and toughness of the resulting materials. This ability to control mechanical properties and performance solely through the initial conditions represents a significant advancement in the design and manufacturing of advanced multiscale. Moreover, we envision that more sophisticated control of reaction-transport driven fronts may enable spontaneous growth of structures and patterns in synthetic materials, inaccessible by traditional manufacturing approaches.