The major force that drives contemporary material research is developing complex functional materials to meet increasing demands of various emerging applications. While many materials—especially in the field of soft matters—seem challenging or even daunting to understand and manipulate, their properties and functions always have molecular origins. Understanding and controlling these complex material systems at the (macro)molecular level will undoubtedly generate new design principles that would ultimately revolutionize material design. In this talk, I will prove this point by using amorphous polymer networks (e.g., elastomer, gel) as a case study. In particular, I will tell three coherent stories to showcase how a deep understanding of the macromolecular network topology enables us to solve three major challenges associated with this important material class, which is typically considered as “a messy system” that is difficult to characterize and understand. In the first story, I will discuss how we developed a simple semi-batch monomer addition method to control topological defects in a variety of polymer networks, and therefore enhance their mechanical properties. Next, I will present a strategy to synthesize polymer networks with photo-switchable topology. This enabled us to externally regulate multiple aspects of material properties in a coherent fashion. Last, I will demonstrate how to develop synthetic systems with highly complex functions by integrating sophisticated biomacromolecular interactions. Specifically, I will show that transient DNA-DNA interactions can facilitate selective cargo transport in a DNA-gated hydrogel. Taken together, I hope to introduce the idea that understanding complex systems at the (macro)molecular level can provide simple solutions to advanced material functions.

Understanding and controlling complex material systems at the (macro)molecular level: Polymer networks as a case study

ACS Spring 2022

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