Marla, Krishna Tej.
Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces.
Degree: PhD, Chemical Engineering, 2004, Georgia Tech
Nanoscale colloidal particles display fascinating electronic, optical and reinforcement properties as a consequence of their dimensions. Stable dispersions of nanoscale colloids find applications in drug delivery, biodiagnostics, photonic and electronic devices, and polymer nanocomposites. Most nanoparticles are unstable in dispersions and polymeric surfactants are added generally to improve dispersability and control self-assembly. However, the effect of polymeric modifiers on nanocolloid properties is poorly understood and design of modifiers is guided usually by empirical approaches. Monte Carlo simulations are used to gain a fundamental molecular-level understanding of the effect of modifiers properties on the thermodynamics and interaction forces of nanoscale colloidal particles. A novel method based on the expanded ensemble Monte Carlo technique has been developed for calculation of the chemical potential of colloidal particles in colloid-polymer mixtures (CPM). Using this method, the effect of molecular parameters like colloid diameter, polymer chain length, colloid-polymer interaction strength, and colloid and polymer concentrations, on the colloid chemical potential is investigated for both hard-sphere and attractive Lennard-Jones CPM. The presence of short-chain polymeric modifiers reduces the colloid chemical potential in attractive as well as athermal systems. In attractive CPM, there is a strong correlation between polymer adsorption and colloid chemical potential, as both show a similar dependence on the polymer molecular weight. Based on the simulation results, simple scaling relationships are proposed that capture the functional dependence of the thermodynamic properties on the molecular parameters. The polymer-induced interaction forces between the nanoparticles have been calculated as a function of the above parameters for freely-adsorbing and end-grafted homopolymer modifiers. The polymer-induced force profiles are used to identify design criteria for effective modifiers. Adsorbing modifiers give rise to attractive interactions between the nanoparticles over the whole parameter range explored in this study. Grafted surface modifiers lead to attraction or repulsion based on the polymer chain length and grafting density. The polymer-induced attraction in both adsorbing and grafted modifiers is attributed primarily to polymer intersegmental interactions and bridging. The location of the thermodynamic minimum corresponding to the equilibrium particle spacing in nanoparticle-polymer mixtures can be controlled by tuning the modifier properties.
Advisors/Committee Members: Dr. J. Carson Meredith (Committee Chair), Dr. Charles A. Eckert (Committee Member), Dr. Clifford L. Henderson (Committee Member), Dr. Peter J. Ludovice (Committee Member), Dr. Rigoberto Hernandez (Committee Member).
Subjects/Keywords: Nanoparticle interaction forces; Colloid chemical potential; Nanoparticle-polymer systems; Colloid-polymer mixtures
to Zotero / EndNote / Reference
APA (6th Edition):
Marla, K. T. (2004). Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7604
Chicago Manual of Style (16th Edition):
Marla, Krishna Tej. “Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces.” 2004. Doctoral Dissertation, Georgia Tech. Accessed March 01, 2021.
MLA Handbook (7th Edition):
Marla, Krishna Tej. “Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces.” 2004. Web. 01 Mar 2021.
Marla KT. Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Mar 01].
Available from: http://hdl.handle.net/1853/7604.
Council of Science Editors:
Marla KT. Molecular Thermodynamics of Nanoscale Colloid-Polymer Mixtures: Chemical Potentials and Interaction Forces. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/7604