Cellulose-based superhydrophobic surfaces and Dynamics of coupled chemical systems
School of Science | Licentiate thesis
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AbstractSuperhydrophobic surfaces can be found in plants, insects, and bird feathers1. Inspired by natural superhydrophobic surfaces, researchers have recently developed and constructed superhydrophobic surfaces in a variety of smart and simple ways. The hydrophilic property of cellulose nanocrystals (CNCs) was modified by the esterification of CNCs with low surface energy chemicals of 2H,2H,3H,3H-Perfluorononanoyl chloride and 2H,2H,3H,3H-Perfluoroundecanoyl chloride, respectively. A stable suspension of nanospherical fluorinated cellulose ester was obtained by using the nanoprecipitation technique. The resulting nanostructured fluorinated cellulose esters was simply coated on a paper surface to gain a superhydrophobic paper surface characterized by a contact angle over 150º. The superhydrophobic paper remained stable even at a high temperature, showing no signs of melting or damage. The hydrophobized paper was characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and static contact angle (CA) measurement. Further, we investigated the size, shape, and amorphicity of nanostructured fluorinated cellulose esters by light scattering (DLS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. The development of economically and ecologically viable strategies for the superhydrophobization of surfaces for the introduction of a self-cleaning property offers a vast variety of interesting applications. Examples include packaging materials, textiles, outdoor clothing, and microfluidic devices. The dynamics of oscillation in chemical reactions as a research field has grown dramatically over the past 50 years and produced thousands of studies on about 70 known chemical oscillators. Oscillating chemical reactions find many applications in physics, biology, physiology, geology, and medicine. The dynamics of the bromate-sulfite-ferrocyanide (BSF) reaction is studied in a well-mixed open chemical reactor, called a continuous stirred tank reactor (CSTR). A CSTR system can be used to investigate the dynamics of outof-equilibrium chemical processes, such as oscillation, bistability, and chaos. This BSF reaction exhibits periodic oscillation as a function of [H+], called pH oscillation. The reaction was carried out at 25 ºC, and the flow rate was 1 and 2 mL/min. The pH oscillation occurs only in a specific range of flow rates. Here, we show regular pH oscillation in a BSF system by utilizing different concentrations under a nitrogen atmosphere. Such a pH oscillator system can be coupled or probed with pH-sensitive systems, and it helps to understand new mechanisms may arise by periodic behavior.
Thesis advisorKostiainen, Mauri
superhydrophobicity, perfluorinated cellulose esters, pH oscillation, BSF system