10.1021/acsomega.7b01443.s002 Md. Anamul Haque Md. Anamul Haque Kei Mito Kei Mito Takayuki Kurokawa Takayuki Kurokawa Tasuku Nakajima Tasuku Nakajima Takayuki Nonoyama Takayuki Nonoyama Muhammad Ilyas Muhammad Ilyas Jian Ping Gong Jian Ping Gong Tough and Variable-Band-Gap Photonic Hydrogel Displaying Programmable Angle-Dependent Colors American Chemical Society 2018 angle-dependent colors photonic gel sheet exhibits tunable photonic PAAm layer thickness bulk geometry gel sheet rocking curves sensor technologies Variable-Band-Gap Photonic Hydrogel Programmable Angle-Dependent Colors One-dimensional photonic crystals light illumination angles angle dependence sheet geometry angle-independent color photonic band gaps sheet surface light modulation angle-dependent behavior photonic hydrogels ductile polyacrylamide photonic materials index variation lamellar bilayer gel rod exhibits band gaps bulk geometries 2018-01-04 00:00:00 Media https://acs.figshare.com/articles/media/Tough_and_Variable-Band-Gap_Photonic_Hydrogel_Displaying_Programmable_Angle-Dependent_Colors/5756337 One-dimensional photonic crystals or multilayer films produce colors that change depending on viewing and light illumination angles because of the periodic refractive index variation in alternating layers that satisfy Bragg’s law. Recently, we have developed multilayered photonic hydrogels of two distinct bulk geometries that possess an alternating structure of a rigid polymeric lamellar bilayer and a ductile polyacrylamide (PAAm) matrix. In this paper, we focus on fabrication of composite gels with variable photonic band gaps by controlling the PAAm layer thickness. We report programmable angle-dependent and angle-independent structural colors produced by composite hydrogels, which is achieved by varying bulk and internal geometries. In the sheet geometry, where the lamellae are aligned parallel to the sheet surface, the photonic gel sheet exhibits strong angle-dependent colors. On the other hand, when lamellae are coaxially aligned in a cylindrical geometry, the gel rod exhibits an angle-independent color, in sharp contrast with the gel sheet. Rocking curves have been constructed to justify the diverse angle-dependent behavior of various geometries. Despite varying the bulk geometry, the tunable photonic gels exhibit strong mechanical performances and toughness. The distinct angle dependence of these tough photonic materials with variable band gaps could benefit light modulation in displays and sensor technologies.