Phase Behavior of Colloidal-Polymer System: Multi-Scale Self-Assembly in Confined Space -Computer Simulation study

• Main Authors: Chung-Shu Chou, 周忠恕
• Other Authors: Tai-Chou Lee
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/97904571008641872000

碩士 === 國立中正大學 === 化學工程研究所 === 99 === Colloidal-polymer system is very complex, and exhibits rich phase structures. It is of fundamental interests and a great challenge to understand the colloidal-polymer mixtures. However, in this complex system, the time and length scales are significantly different between colloidal particles and polymer molecules. These bring a huge challenge for computer simulation studies. Therefore, in this study, we use the atomistic level method to correct the length and time scale differences, and then use molecular dynamics simulation package DL_Poly to calculate the trajectories of all particles, including speed and position at each time step. Radial distribution function (RDF) can be obtained. Effective potential, structure factor, and other physical properties can then be derived. Finally, Tecplot and CrystalMaker were then used to show the equilibrium structure and process of all trajectories. In this simulation, two potential forms were adopted：Lennard-Jones potential and Morse potential. These interactions were considered for polymer chains：Bond stretching potential, bond angle potential, and bond torsion potential. In this thesis, we carried out five different stage experiments, from simple and easy to predict, gradually added to the different elements, finally to a system that consisted of colloid and polymer suspended in confined space with polymer brushes grafted on the walls. Thermodynamic properties and dynamic behaviors can then be examined. From these experiments, as the volume fraction of colloidal particles increases, the particles will aggregate due to depletion effects. At stage two, when polymer brushes were grafted onto one side of the wall (boundary), the grafting density will affect the structure of the polymer brushes. At stage three, colloidal particles were added. It was found that colloids were trapped inside the polymer brushes once they were close to the wall. While polymer melt was further included in the calculation (stage four), the polymer melt will aggregate at high polymer brush grafting density. Finally, when polymer brushes were grafted on both sides of the walls, the aggregated polymer melt will re-dispersed in the system.