Monte Carlo studies of three-dimensional chains on a lattice: The equation of state and segment density profile near a repulsive wall.
Item
-
Title
-
Monte Carlo studies of three-dimensional chains on a lattice: The equation of state and segment density profile near a repulsive wall.
-
Identifier
-
AAI9315465
-
identifier
-
9315465
-
Creator
-
Hertanto, Agung Eko.
-
Contributor
-
Adviser: Ronald Dickman
-
Date
-
1993
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Physics, General
-
Abstract
-
The equation of state and conformational properties of polymer chains on a regular lattice are investigated using Monte Carlo simulations. Various chain systems are studied: athermal monodisperse and polydisperse linear chains, non-athermal linear chains, and chains with various branch-structures. The chain-length varies from N = 10 to 150. In these simulations, the test-chain insertion method is employed to obtain the insertion factor in the low density regime and to determine the theta-temperature, and the repulsive wall method is used to determine the equation of state in the high density regimes.;This dissertation focuses on comparison between simulation results and predictions of Flory and Flory-Huggins mean-field theories, and Freed's n-vector model. The results indicate that the Freed's n-vector model provides the best estimate of the osmotic pressure at various densities and solvent qualities. A discrepancy exists for chains with branch structures.;Other conformational properties investigated are the end-to-end distance and the segment density profile near a repulsive wall. Scaling techniques are employed to obtain the scaling exponent {dollar}\nu{dollar} and the density dependence of the osmotic pressure. Monte Carlo results support de Cloizeaux' scaling law for the pressure. The effect of confinement on the equation of state and the end-to-end distance is also studied for chains at finite concentration. To study the effect of an interface, an analytical calculation is performed to determine the density profile of Gaussian chains adjacent to a repulsive wall. It shows that {dollar}\rho \propto{dollar} z{dollar}\sp2{dollar} for z {dollar}\to{dollar} 0, where z is the distance from the wall. Edwards' model is also used to represent a polymer chain. In this model, the renormalization group equation and the {dollar}\epsilon{dollar} expansion (up to first order) are presented to determine the scaling exponent of {dollar}\rho{dollar}(z) for z {dollar}\to{dollar} 0. Monte Carlo results also indicate the scaling behavior for athermal chains. For non-athermal chains, a complication arises due to the temperature dependence, which is not represented in Edwards' model.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
