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Monte Carlo simulations of flexible polymeric chains in solution
Abstract
Dilute and semidilute concentrations of polymeric solutions are often used to elucidate fundamental characteristics of the molecules and specific interactions with a solvent. However, the theories that describe these regions of concentration have not been able to predict the values and scaling relationships observed in such experiments. This thesis uses both lattice based and continuous space Monte Carlo computer simulations to investigate these regions of concentration in three ways: (1) Evaluate the lattice and continuous space models for their ability to predict experimental scaling relationships; (2) attempt to provide values from the equation of state that may be compared with experimental data, and (3) calculate the scattering function for an amorphous system to investigate local organization and to provide comparisons with solution X-ray and neutron scattering data. Results from the lattice simulations were found to follow the trends predicted by mean field lattice theories at dilute and semidilute concentrations. This means that the approximations made in obtaining numerical results from the theories are acceptable. However, as mean field approximations are known to be invalid at these concentrations, lattice models in general are inapplicable to dilute and semidilute concentrations. The continuous space models investigated here approximate the trends from experimental data in dilute and semidilute concentrations better than lattice models, but still do not provide values from the equation of state that agree with experiment. The investigation of higher concentrations, greater than about 5% bead volume, was performed in an isobaric-isothermal ensemble since the pair correlation function of the canonical ensemble is no longer sufficient at such concentrations. While the development of simulations using the isobaric-isothermal ensemble is in its nascent state, these simulations appear to offer a powerful apparatus by which to investigate the thermodynamic properties of a system. A new method was developed by which to calculate the scattering function $S(q)$ efficiently from a large system of amorphous chains. Hence, the results for models representing polymeric chains in solution may be compared with experimentally determined data. The agreement of results from these simulations with X-ray and neutron scattering data is encouraging.
Subject Area
Physical chemistry|Chemistry
Recommended Citation
Starry, Scott K, "Monte Carlo simulations of flexible polymeric chains in solution" (1990). Doctoral Dissertations Available from Proquest. AAI9035407.
https://scholarworks.umass.edu/dissertations/AAI9035407