Interfacial Engineering Approach to Pattern Resilient Polymer Photonic Crystals with Temperature-Responsive Optical Properties

Planar, 1D photonic crystals (1D-PCs) are stacks of alternating layers with different refractive indices, which can reflect specific wavelengths of light through the formation of a photonic bandgap. Typical systems for 1D-PC fabrication possess relatively limited thermal and/or chemical stabilities and may require several steps for producing patterned features. Additionally, enabling stimuli-responsive behaviors in 1D-PCs are often achieved through relatively complex chemistries that might be difficult to scale-up due to associated cost and energy consumption, presenting challenges toward their implementation in practical systems. Herein, through sequential depositions of phenolic resin (resol) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), two low-cost chemical reagents which are broadly used in industry, bright 1D-PCs are prepared with high thermal and chemical stability at long exposure times. Furthermore, spatial differences in the reflectance behavior of the 1D-PCs and thus resulted patterns are demonstrated through a simple, generalizable interfacial engineering approach that controls the surface wettability of PVDF-HFP layer. Stimuli-responsive behavior is imparted into the 1D-PC system by leveraging the semicrystalline nature of PVDF-HFP to provide on-demand switchable light-reflecting behaviors upon exposure to elevated temperatures. Overall, this work demonstrates a simple and efficient technique to develop 1D-PCs with excellent stability, ease of patterning, and thermoresponsive reflectance from low-cost precursors, potentially enabling their broader use in a wide array of nanotechnological applications.