Dissertation > Excellent graduate degree dissertation topics show

Effects of Long-range Interaction and Confinement on Polymer Chain Conformation and Morphology

Author: XuHui
Tutor: ZhangHongDong
School: Fudan University
Course: Polymer Chemistry and Physics
Keywords: Polyelectrolyte Monte Carlo simulation Ewald summation Two - block copolymer TDGL equation Closed spherical shell
CLC: O631.3
Type: Master's thesis
Year: 2010
Downloads: 20
Quote: 0
Read: Download Dissertation

Abstract

With ionized charged groups in the main chain of the polyelectrolyte, ionization occurs in a polar solvent, with a charge in the main chain, and the release is known as counter-ions with the molecular ion of the opposite charge. As compared to the polyelectrolyte electrically neutral polymer is more electrostatic interactions between the influence of the long-range interactions, will exhibit more complex conformational behavior polyelectrolyte in solution compared to the electrically neutral polymer, its solution viscosity, pressure, and other physical properties will not change significantly. The polyelectrolyte so different from the general nature of the polymer and the consequent application in the fields of energy, biotechnology, environmental protection, has attracted the attention of many researchers. The polyelectrolyte nature can be traced back to the 40s of the last century, the earliest and still is a major research focus. The morphology of the polymer under the conditions of behavior is also one of the researchers focus of attention as another factor affecting the polymer morphology, space is limited. Block copolymers due to the entropy of mixing between its block is very small under normal circumstances, multi form thermodynamically immiscible, and phase separation occurs. The phase separation behavior, not only the interaction parameter z block ratio of each component, and the polymer chain by space restrictions limit relevant. The constrained conditions compared to a generally flat space, curved space within the polymer is also subject to the curvature of the analog current in the phase separation in the ball surface and a block copolymer of the ball body, has been reported. In this article, the first chapter introduces the polyelectrolyte solution research progress and the basic theory. In the simulation work has been reported on the polyelectrolyte, we found that Most of the simulation work is generally only concerned with a two specific conformation, or only consider the impact of temperature on the electrostatic energy. Taking into account the nature of the solvent will also affect the conformation of the polyelectrolyte, we also want to consider the temperature of the electrostatic and solution properties. In the second chapter, we use the Monte Carlo method to simulate lattice chain model of the single-chain system polyelectrolyte solution. In our model, each segment in the main chain, with an equal amount of positive charge, each of the counter-ions with the equal amount of negative charge, and the solution generally electrically neutral. Set the solubility parameter χ = akBT (a> 0), Ewald summation calculation electrostatic energy, △ E * = △ E / KnT, so we can by changing the temperature, while changing the nature of the solvent, and the size of the electrostatic interactions investigated electrostatic energy and the nature of the solvent varies with temperature changes in the nature of poly electrolyte chain. We found that at low temperatures when, χ large chain is in a poor solvent, electrostatic interaction effect is also apparent when the chain is long enough to form a beaded conformation; as the temperature rises, conformation sequential change to collapse condensing the sphere, random coil, etc.; tensile coiled conformation is formed at high temperature conditions. The main content of the third chapter is limited closed spherical shell within two block copolymer phase separation TDGL simulation. Our work is phase separation behavior within a closed spherical shell of a certain thickness. Dynamics simulation, we found that when the surface of the block is not selective, then the radius of the spherical shells and thickness affect the behavior of the phase separation kinetics of phase separation process in line with the general block copolymer phase separation kinetics theory. When the surface of the block selective, the radius of the spherical shell in the influence of the morphology of the phase separation is small, the more evident the influence of the thickness of the surface of selective size and spherical. The larger the difference when the spherical shell thickness is the greater, the greater the role of surface points of the phase behavior of the non-selective surface conditions. Phase separation kinetics influenced by surface selective process in the early time, with the conduct of the process of phase separation, the space limiting effect to rise slowly, and the final phase separation of the result is both balanced result.

Related Dissertations

CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
© 2012 www.DissertationTopic.Net Mobile