Data_Sheet_1_pH-Responsive Aqueous Bubbles Stabilized With Polymer Particles Carrying Poly(4-vinylpyridine) Colloidal Stabilizer.pdf

Free radical dispersion polymerization was conducted to synthesize near-monodispersed, micrometer-sized polystyrene (PS) particles carrying pH-responsive poly(4-vinylpyridine) (P4VP) colloidal stabilizer (P4VP-PS particles). The P4VP-PS particles were extensively characterized in terms of morphology, size, size distribution, chemical composition, surface chemistry, and pH-response using optical and scanning electron microscopies, elemental microanalysis, X-ray photoelectron spectroscopy, laser diffraction particle size analysis, and zeta potential measurement. The P4VP-PS particles can work as a pH-responsive stabilizer of aqueous bubbles by adsorption at the air-water interface. At and above pH 4.0, where the particles have partially protonated/non-protonated P4VP stabilizer with relatively hydrophobic character, particle-stabilized bubbles were formed. Optical and scanning electron microscopy studies confirmed that the P4VP-PS particles were adsorbed at the air-water interface of the bubbles in aqueous media. At and below pH 3.0, where the particles have cationic P4VP stabilizer with water-soluble character, no bubble was formed. Rapid disruption of the bubbles can be induced by decreasing the pH; the addition of acid caused the in situ protonation of pyridine groups in P4VP, which impart water-soluble character to the P4VP stabilizer, and the P4VP-PS particles were desorbed from the air-water interface. The bubble stabilization/destabilization cycles could be repeated at least five times.

自由基分散聚合技术被应用于合成近单分散、微米级的聚苯乙烯（PS）颗粒，并负载pH响应性的聚（4-乙烯基吡啶）（P4VP）胶体稳定剂（P4VP-PS颗粒）。通过光学显微镜和扫描电子显微镜、元素微分析、X射线光电子能谱、激光衍射颗粒尺寸分析和ζ势测量等手段，对P4VP-PS颗粒进行了广泛的表征，包括形貌、尺寸、尺寸分布、化学成分、表面化学和pH响应性。P4VP-PS颗粒可通过在气-水界面吸附的作用，充当水泡的pH响应性稳定剂。在pH 4.0及以上的条件下，颗粒表面部分质子化/非质子化的P4VP稳定剂表现出相对疏水性，从而形成颗粒稳定的泡。光学显微镜和扫描电子显微镜的研究证实，在水中，P4VP-PS颗粒吸附于气泡的气-水界面。在pH 3.0及以下的条件下，颗粒表面的阳离子P4VP稳定剂具有水溶性，此时不会形成气泡。通过降低pH值可以迅速破坏气泡；加入酸导致P4VP中的吡啶基团原位质子化，赋予P4VP稳定剂水溶性，P4VP-PS颗粒从气-水界面解吸。气泡的稳定/去稳定循环至少可以重复五次。