Atomistic simulation of macromolecules

Abstract

This thesis focuses on the atomistic simulation of polymers/dendrimers material properties and development/applications of Monte Carlo methods for macromolecules. The main topics and their outlines are listed as following. 1) Structures and properties of crystalline polymers from theory. Although crystalline polymers such as nylon are important industrial materials, it is difficult to get the details of the various structures/properties and the conversion between them from the experiment. Using molecular modeling, we successfully predicted the complicated structures/properties and illustrated the process of forming the polymer crystal and conversion mechanism among those structures. 2) Packing mechanism of self-assembly dendrimer balls with soft coronas. Using the vibrational density of state (DoS) derived from molecular dynamic simulations, we investigate the free energy of the liquid crystal formed by soft dendrimer balls. We find that the preferred lattice for soft balls is different from the hard balls and illustrate the mechanism. 3) Development of CCBTX Monte Carlo method for polymer and dendrimer. Although computer simulation has developed as a powerful research tool to study polymer/dendrimer materials properties recently, it has been hampered by the difficulties of sampling amorphous polymer/dendrimer configurations efficiently. We develop the efficient Continuous Configurational Biased TX (CCBTX) method to generate high-quality amorphous polymer and dendrimer atomistic structures directly. The code is implemented in C++ and ported in python environment, which provides friendly interface. 4) Thermodynamic functions, critical exponents, and theta temperatures of polymer chains from CCBB Monte Carlo method. We examine the thermodynamic properties (entropy, energy, end-to-end distance) of isolated polymer chains with the Monte Carlo method.