Preparation Of Polystyrene Colloidal Particles And Research On Interface Electrical Properties

Recently, Photonic Crystals have attracted much attention in the world for widely application prospect. At present, photonic crystals for microwave range can be prepared by processing semiconductor precisely, and have got elementary application. But it is very difficult to prepare photonic crystals in visible and near-infra-red range with this method. In solution, if the charge density and particle concentration are in a good situation, monodisperse colloidal particle spheres with charge in the interface can be self-assembled into close-packed face-centered cubic or body-centered cubic periodic structure through electrostatic interaction, resulting in forming colloidal crystals. Colloidal crystals have become a simple and effective method for synthesis of three-dimensional photonic crystals of visible and near-infra-red range because their crystal lattice sizes are just in sub-micron range. With this method, the preparation of microspheres with uniform size and high stability is one of the most critical technical problems. Therefore, on the basis of the conclusions drawn by predecessors, the preparation of polystyrene colloidal particles and their interface electrical properties have been studied in this paper. The research work could be divided into the following three parts.1. The preparation of uniform colloidal particles of polystyreneIn this part, polystyrene colloidal particles were prepared by soap-free emulsion polymerization. The results showed that it was a useful method for the preparation of uniform polystyrene particles with diameters ranging from 400 to 800 nm.The polymerization time was more than 20 hours in traditional methods, while a conclusion could be obtained that the polymerization time could be reduced to 12 hours by researching the relation between polymerization time and PS microsphere diameters as well as size distribution. In order to prepare the PS microspheres with controllable sizes, the influence factors on PS microsphere diameter and sizedistribution have been investigated. The results revealed: When other factors were kept constant, the diameter of PS microspheres increased in line with increasing monomer concentration. When the concentration of initiator reagent increased, the diameter of PS microspheres decreased at first and then increased with a broad size distribution. Polymerization temperature was a very important factor which intensively affected the PS particles size. The research showed that monodisperse PS microspheres could be well prepared by soap-free emulsion polymerization at the reaction temperature from 55 to 80 centigrade and the microspheres with the largest diameters could be obtained at the temperature of 64 centigrade. Ionic strength was also an important factor on PS particles size and size distribution. The diameter of PS microspheres increased with increasing ionic strength, but the increase of ionic strength could lead to broadening on size distribution. Thus, when preparing certain size PS microspheres, all factors mentioned above should be considered comprehensively.2. The interface electrical properties of polystyrene uniform colloidal particlesIn this part, by researching on the variable curve of ζ-potential along with pH in different ionic strength, we concluded that the polystyrene colloidal particles prepared by soap-free emulsion polymerization were relatively stable. The particles had an isoelectric point (IEP) in the strong acid range. Their zeta-potentials were invariable with the pH varied from 6 to 10.5, the constant ζ-potentials value provided an evidence for getting the suitable conditions for storing polystyrene particles, and the constant also implied that the PS microspheres could be used as model particles for its stable ζ-potential. At certain ionic strength, the ζ-potential increased with the size of polystyrene microspheres increased. Generally speaking, the ζ-potential will decrease as the ionic strength increased, but in this work we found that the ζ-potential at ionic strength of 10-3mol/l was anomalously larger than that at lowe...