Nature uses proteins to create biomaterials that range from spider silk to human tissue. Synthetic materials that utilize proteins have potential as biodegradable plastics and composites (protein-polymer networks). It is critical to understand the protein design parameters that determine the desired material outcomes in protein-polymer networks. In addition to protein structure, the topology of the polymer network serves an important role in the mechanical response of these materials. While the mechanical properties of these materials can be experimentally determined, computational simulations can provide critical insights into the mechanical response of proteins as they unfold within a network structure. The transformative scientific aspects of our proposal are (i) the synthesis and computational simulations of de novo designed proteins and their respective protein-polymer networks and (ii) techniques for mechanical characterization of polymer-protein networks on the microscale that will accelerate the discovery and deployment of proteins as junctions in polymer networks for biohybrid plastics and engineering bioplastics. Additionally, 3D printing will enable the distributed manufacturing of parts, as well as custom designs that can be created by architects, engineers, and other users. This project addresses the national need for advanced manufacturing methods that are more sustainable built environments via reduced carbon footprint (reduced transport costs and greener production) and chemical circularity (chemical recycling of protein-based materials). This project also addresses the national need to develop the next generation of a highly skilled and diverse future workforce.