Physics of architecturally complex polymers and networks

A bottlebrush polymer consists of a long linear backbone densely grafted with many relatively short side chains. Unlike classical linear polymers, the bottlebrush architecture enables mechanical, biophysical, and biochemical properties to be encoded independently, making bottlebrush polymers as a versatile platform for soft (bio)materials design and innovation. I will describe my lab’s recent efforts to understand and apply bottlebrush polymers. I will begin with a theoretical framework for their molecular structure. Corroborated with experiments, we discover that, in some cases, the bottlebrush backbone can fold to store length regardless of the strong steric repulsion among highly overlapping side chains, a finding that challenges prevailing view. I will show that using this “foldable” bottlebrush polymers as network strands offers a universal strategy to decouple stiffness and extensibility in single-network elastomers, the fundamental component of all kinds of polymer networks. I will then highlight applications of (foldable) bottlebrush polymers as individual molecules, supramolecular assemblies, resins for additive manufacturing, and cell-instructive biomaterials. I will also discuss open questions in bottlebrush polymer physics, including glass transition, molecular dynamics, entanglements, and nanoparticle transport within bottlebrush matrices.