Effect of Grafting Density on the Crystallization Behavior of Molecular Bottlebrushes

Molecular bottlebrushes (mBB) are a class of materials that present a rich landscape of architectural parameters that affect their behavior in solution, melts, and upon crystallization. Understanding the influence of architectural parameters on crystallization behavior is important for developing applications for these interesting polymer materials. This presentation will discuss the grafting density and branching effects on mBB crystallization. We show that the crystallization behavior of side chains is strongly impacted by grafting them to the backbone, slowing crystallization kinetics and increasing nucleation density. At low grafting densities, bottlebrush side chains are under soft confinement, with this confinement alleviated as grafting density is increased. Further modifying the molecular architecture by introducing a branched backbone further hinders the crystallization kinetics of these molecules. In both cases, the grafting density also increases the retention of melt memory above the equilibrium melting temperature, indicating that the bottlebrush architecture retains the conformation of side chains deep into the melt state.