CAREER: Multi-scale Effects of Polymer Network Topology on Mechanical Properties

This Faculty Early Career Development Program (CAREER) award will advance fundamental understanding of why soft materials fracture and fail by considering the multi-scale structures that arise within polymer networks. Soft materials are widely used in large-volume applications such as tires, vibration isolation components, and seals, as well as in emerging technologies including biomedical devices and human–machine interfaces. Despite their widespread use, these materials often experience fracture and fatigue that limit their reliability and service lifetime, contributing to material waste, environmental pollution, and increased economic costs. The mechanical weakness of many soft materials originates from the topology of polymer networks—that is, how polymer chains connect, entangle, and organize in space. While prior studies have shown that molecular-scale features can influence resistance to fracture and fatigue, many engineering soft materials also contain structures at larger length scales, including nanoscale domains and embedded particles. The interactions between polymer topology and these multi-scale structures remain poorly understood, particularly in systems where features across several length scales simultaneously influence mechanical performance. This project will establish fundamental principles that connect polymer network topology, hierarchical structure, and mechanical durability in soft materials. In addition to advancing basic scientific knowledge, the results will support the development of more reliable and sustainable soft materials for technologies that rely on flexible mechanical components. This CAREER award will also support an integrated educational program that trains students in mechanics and polymer science, develops learning modules linking molecular structure to material properties, and engages students in interdisciplinary research experiences. The CAREER project will support research aimed at establishing a mechanistic framework that links polymer network topology, multi-scale structural organization, and resistance to fracture and fatigue. The central objective is to determine how topological features of polymer networks control the formation of hierarchical structures and how these structures govern mechanical failure in soft materials. To achieve this goal, the research will combine controlled synthesis of polymer networks with systematic characterization of structure and mechanical performance across multiple length scales. The work will examine three interconnected themes: differentiation of entanglement types as a tunable topological variable, design of nanoscale structures through topological control of polymer networks, and synergistic interactions between polymer topology and nanoparticles. Structural characterization methods will be used to quantify organization from the molecular scale to mesoscale domains, while mechanical testing will measure resistance to fracture and fatigue under well-controlled loading conditions. These measurements will be interpreted using fracture mechanics concepts that describe stress concentration and crack propagation across multiple structural scales. By integrating synthesis, structural characterization, and mechanical analysis, the project will establish predictive relationships connecting polymer topology, hierarchical structure, and material durability. The resulting framework will provide new insight into the mechanisms governing fracture in soft materials and will guide the design of polymer networks with improved resistance to mechanical failure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.