Siegwardt Lukas, Glößner Victoria, Boehm Anna, Schneider Marc, Gallei Markus
Polymer Chemistry, Saarland University, Saarbrücken 66123, Germany.
Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken 66123, Germany.
ACS Appl Mater Interfaces. 2024 Feb 28;16(8):10722-10735. doi: 10.1021/acsami.3c17974. Epub 2024 Feb 13.
While stimuli-responsive structural colors are commonly found in nature, mimicking these in artificial materials is challenging. Dynamically switchable and tunable coloration, however, is in high demand in widespread fields of applications, including advanced display and monitoring technologies, smart sensing, and anticounterfeiting. This work reports a scalable protocol for the synthesis of tailor-made core-shell particles and subsequent processing to opal films with iridescent, pH-responsive, and mechanochromic structural color. Novel monodisperse core-shell architectures based on hard polystyrene core particles are synthesized via stepwise emulsion polymerization in a starved-feed mode. The incorporation of 4-vinylpyridine and methacrylic acid as functional comonomers in the soft particle shell facilitates pH-responsive swelling and deswelling. Mechanically stable and well-ordered colloidal crystal films are obtained by the self-assembly of the particles during processing with the powerful melt-shear organization technique. Thereby obtained opal films show Bragg-scattering at the colloidal crystalline structure and exhibit brilliant green-turquoise to blue-violet reflection colors, dependent on the angle of view and illumination. Upon changes in the pH value or mechanical deformation, the reflected wavelength shifts by more than 100 nm, leading to intriguing changes in the visible structural color. Excellent reversibility is achieved by the subsequent application of a convenient UV cross-linking strategy, corroborating the high application potential of these advanced functional materials.
虽然刺激响应性结构色在自然界中普遍存在，但在人工材料中模仿它们具有挑战性。然而，动态可切换和可调谐的显色在包括先进显示和监测技术、智能传感和防伪等广泛的应用领域中有着很高的需求。这项工作报道了一种可扩展的方案，用于合成定制的核壳颗粒，并随后将其加工成具有虹彩、pH响应和机械变色结构色的蛋白石薄膜。基于硬聚苯乙烯核颗粒的新型单分散核壳结构通过饥饿进料模式下的逐步乳液聚合合成。在软颗粒壳中引入4-乙烯基吡啶和甲基丙烯酸作为功能共聚单体，有助于pH响应性的溶胀和去溶胀。通过使用强大的熔体剪切组织技术在加工过程中使颗粒自组装，获得了机械稳定且有序的胶体晶体薄膜。由此获得的蛋白石薄膜在胶体晶体结构处显示布拉格散射，并根据视角和照明呈现出从亮绿宝石色到蓝紫色的反射颜色。当pH值或机械变形发生变化时，反射波长移动超过100nm，导致可见结构色发生有趣的变化。通过随后应用方便的紫外交联策略实现了优异的可逆性，证实了这些先进功能材料的高应用潜力。
