Research Seminar Abstract

Photonic crystals (PC) are periodic nanostructures engineered in nature to reflect different wavelengths of light for camouflage, signaling, photosynthesis, and heat control. These natural photonic crystals can be mimicked through the self-assembly of block copolymers (BCPs). The challenge of BCP self-assembly to photonic crystals is that chain entanglement often impedes the self-assembly of linear BCPs into a periodic structure of required domain size. By engineering the macromolecular architecture to reduce the BCP’s capacity for chain entanglement in order to enable self-assembly to large nanostructures, it is possible to provide an approach to polymer based visible-light reflecting PCs. For example, bottlebrush BCPs are often used to reach domain sizes large enough to reflect visible wavelengths of light and beyond. However, recently it has been shown that rigid, yet linear, BCPs can self-assemble to photonic crystals that reflect wavelengths of light across the visible light spectrum and into the near infrared depending on the molecular weight of the polymer.

These rigid linear polymers have a unique dendritic architecture that promotes interesting dynamic melt and mechanical properties. These dendritic polymers possess many characteristics that are similar to those of bottlebrush polymers when compared to the responses that a non-rigid, linear polymer would produce. These responses include a rod-like conformation, a reduced capability for chain entanglement, and lower glassy moduli compared to non-rigid, linear polymers. Further, dendritic BCPs possess high free energy parameters, as well as glass transition temperatures below melt extrusion 3D printing operating conditions and are able to self-assemble into photonic crystals during the process of 3D printing. Lastly, varying the molecular weight of the BCP allows selective reflection of the PCs for wavelengths of light across the visible spectrum.