Synthesis of polystyrene nanoparticles and microstructures of nanoparticle film

• Main Authors: Chi-Jen Lo, 羅啟仁
• Other Authors: Tai-Chou Lee
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/57087692174209711224

碩士 === 國立中正大學 === 化學工程所 === 97 === Nanoparticles have major applications in the fields of food, printing, liquid crystal and drug release. These particles can also generate ordered structures, so called photonic crystals (PCs), which can enhance the optical property in the device such as fiber, laser and wave guide. Among all fabrication approaches, two processes are generally used: lithography and self-assembly. Lithography has been recognized as an excellent method to produce large area defect-free 3D PCs due to its scalability and controllability, but this process is limited by its expensive equipment that ordinary laboratory cannot afford. On the other hand, self-assembly becomes a better method in fabrication of 3D PCs in the lab. In order to control the sizes of polystyrene (PS) nanoparticles, we carried out the PS synthetic experiments. PCs were then prepared by sonication-assisted casting (SAC). Additionally, microstructure evolution during solvent evaporation is of fundamental interest. Therefore, we designed an environmental chamber that can maintain suitable experimental conditions. This thesis is mainly divided into three parts: synthesis of PS nanoparticles, fabrication of PCs by SAC and design of environmental chamber. Surfactant-free emulsion polymerization was used to synthesize PS nanoparticles of diameters between 30-1000 nm, by changing the concentration of styrene, 4-styrenesulfonic acid sodium salt, and sodium chloride. They served as monomers, nuclei, and the salt that varied the ionic strength, respectively. Diameter and distribution of particles were characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). PCs made of PS nanoparticles with diameters between 200 nm-1000 nm was fabricated by SAC. Different structures such as hexagonal, cubic, and random packing can be obtained, by adjusting concentration, volume and solvent of precursor. High-quality PCs, using 100 μL and 24 mg/mL of precursor, were prepared on the 1 cm2 glass substrate. SEM cross-section image shows the face centered cubic (FCC) array. Peak position of the UV-Vis spectrum (absorption > 30%) agrees with the Bragg’s-Snell law. Additionally, the diameter and quality of PCs can also be qualitatively determined from the scattering stripes by home-built of solid state film light scattering (SSL-LS). Environmental chamber is comprised of a temperature controller and an automatic dispensing system. The temperature can be controlled from room temperature to 300℃, and a steady experimental environment can be reached in 20 min. This chamber is able to dispense a desired volume of precursor and to maintain constant dry speed. We can, in theory, utilize an in-situ grazing incidence x-ray scattering (IsGIXS) with high-flux synchrotron radiation source to study structure evolution of thin film formation during solvent evaporation. The further applications of PCs are the ultimate goal. For example, utilize it as a template to fabricate porous films or exploit the unique property of photonic band gap of PCs to enhance the absorption of particular wavelength in material, more investigations need to be done.