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You searched for subject:(Expanded ensemble). Showing records 1 – 2 of 2 total matches.

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University of Waterloo

1. Pansri, Siriporn. Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method.

Degree: 2018, University of Waterloo

In this thesis, the Expanded Ensemble Density-of-States (EXEDOS) method - a combination of the Wang-Landau and Expanded Ensemble Monte Carlo algorithms is employed to investigate spatial conformations of a polymer chain under spherical confinement. The study focuses on flexible chains up to 600 monomers and semi-flexible chains with various stiffnesses up to 300 monomers in length. Spatial conformations of the polymer are studied, using a simple pearl-necklace chain model of varied diameter and stiffness, as well as the model of fused-sphere chain. To test the applicability of the EXEDOS method, the confinement free energy was calculated for ideal and non-ideal flexible chains inside spheres of sizes smaller than their unconfined size. For ideal chains, the power-law dependence of the free energy on a confining radius is in excellent agreement with previous theoretical predictions. For self-avoiding chains at intermediate concentrations, the dependence of free energy on concentration deviates from that predicted by the blob scaling theory, most likely due to the finite size effects. At high concentrations, a stronger dependence of free energy on concentration is observed, compared to that obtained at intermediate concentrations. The density profile of a self-avoiding flexible chain was also studied, showing that at sufficiently high concentrations, excluded volume interactions push the chain close to the confining surface, leading to an oscillation in monomer number density near the surface. In semi-flexible chains, bending energy experiences largest changes at low densities as the polymer folds to conform the confining sphere, and at high density its growth slows down as the chain starts forming ordered layer near the surface. We observe isotropic-nematic (I-N) transition for all considered polymer chains. The I-N transition of more flexible chains happens at higher densities than that of stiff chains. All chains form disordered to imperfect helicoildal structures, and at densities above the I-N transition, the structure with four +1/2 defects is observed in all considered chains. However, the polymer spatial arrangement is far from an ideal tetrahedral and tennis ball structure. The EXEDOS algorithm is further extended to investigate the effects of steric hindrance on the structure in a semi-flexible chain, spherically confined at various concentrations. Semi-flexible chains modeled as pearl-necklace chains with ratio of diameter to bond length d/a less than or equal to 0.5 did not develop ordered structures at any considered concentrations, while chains with d/a = 0.8 and d/a = 1, formed imperfect helicoildal structures. On the contrary, a semi-flexible fused-sphere chain with monomer overlap (d/a = 2) forms distinct helicoildal structures, when confined in- side a small sphere of the same size as the pearl-necklace chains with d/a = 0.8 and 1. The evolution of ordered parameters with concentration suggests that during the transition from disordered to ordered configuration, the…

Subjects/Keywords: DNA; Monte Carlo; Wang-Landau; Expanded Ensemble Density-of-States; Spherical confinement; polymers

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Pansri, S. (2018). Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method. (Thesis). University of Waterloo. Retrieved from http://hdl.handle.net/10012/13012

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Pansri, Siriporn. “Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method.” 2018. Thesis, University of Waterloo. Accessed October 20, 2020. http://hdl.handle.net/10012/13012.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Pansri, Siriporn. “Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method.” 2018. Web. 20 Oct 2020.

Vancouver:

Pansri S. Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method. [Internet] [Thesis]. University of Waterloo; 2018. [cited 2020 Oct 20]. Available from: http://hdl.handle.net/10012/13012.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pansri S. Spherically Confined Polymers: Monte Carlo Simulations with Expanded Ensemble Density-of-States Method. [Thesis]. University of Waterloo; 2018. Available from: http://hdl.handle.net/10012/13012

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Georgia Tech

2. Quant, Carlos Arturo. Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry.

Degree: MS, Chemical Engineering, 2004, Georgia Tech

The potential applications of dispersed and self-assembled nanoparticles depend critically on accurate control and prediction of their phase behavior. The chemical potential is essential in describing the equilibrium distribution of all components present in every phase of a system and is useful as a building block for constructing phase diagrams. Furthermore, the chemical potential is a sensitive indicator of the local environment of a molecule or particle and is defined in a mathematically rigorous manner in both classical and statistical thermodynamics. The goal of this research is to use simulations and experiments to understand how particle size and composition affect the particle chemical potential of attractive nanoparticle-polymer mixtures. The expanded ensemble Monte Carlo (EEMC) simulation method for the calculation of the particle chemical potential for a nanocolloid in a freely adsorbing polymer solution is extended to concentrated polymer mixtures. The dependence of the particle chemical potential and polymer adsorption on the polymer concentration and particle diameter are presented. The perturbed Lennard-Jones chain (PLJC) equation of state (EOS) for polymer chains1 is adapted to calculate the particle chemical potential of nanocolloid-polymer mixtures. The adapted PLJC equation is able to predict the EEMC simulation results of the particle chemical potential by introducing an additional parameter that reduces the effects of polymer adsorption and the effective size of the colloidal particle. Osmotic pressure measurements are used to calculate the chemical potential of nanocolloidal silica in an aqueous poly(ethylene oxide) (PEO) solution at different silica and PEO concentrations. The experimental data was compared with results calculated from Expanded Ensemble Monte Carlo (EEMC) simulations. The results agree qualitatively with the experimentally observed chemical potential trends and illustrate the experimentally-observed dependence of the chemical potential on the composition. Furthermore, as is the case with the EEMC simulations, polymer adsorption was found to play the most significant role in determining the chemical potential trends. The simulation and experimental results illustrate the relative importance of the particles size and composition as well as the polymer concentration on the particle chemical potential. Furthermore, a method for using osmometry to measure chemical potential of nanoparticles in a nanocolloid-mixture is presented that could be combined with simulation and theoretical efforts to develop accurate equations of state and phase behavior predictions. Finally, an equation of state originally developed for polymer liquid-liquid equilibria (LLE) was demonstrated to be effective in predicting nanoparticle chemical potential behavior observed in the EEMC simulations of particle-polymer mixtures. Advisors/Committee Members: Meredith, Carson (Committee Chair), Ludovice, Peter (Committee Member), Nenes, Athanasios (Committee Member).

Subjects/Keywords: Attractive particle polymer systems; Chemical potential; Colloids; Colloidal dispersions; Expanded ensemble; Lennard-Jones; Membranes; Monte Carlo method; Nanocolloid; Nanoparticles; Osmometry; PEO; Polyethylene oxide; Polymers; Silica; Simulation; Polymers; Colloids; Nanoparticles; Phase transformations (Statistical physics)

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Quant, C. A. (2004). Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7616

Chicago Manual of Style (16th Edition):

Quant, Carlos Arturo. “Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry.” 2004. Masters Thesis, Georgia Tech. Accessed October 20, 2020. http://hdl.handle.net/1853/7616.

MLA Handbook (7th Edition):

Quant, Carlos Arturo. “Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry.” 2004. Web. 20 Oct 2020.

Vancouver:

Quant CA. Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry. [Internet] [Masters thesis]. Georgia Tech; 2004. [cited 2020 Oct 20]. Available from: http://hdl.handle.net/1853/7616.

Council of Science Editors:

Quant CA. Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry. [Masters Thesis]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/7616

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