Date of Award
Doctor of Philosophy (PhD)
Biomedical and Chemical Engineering
micelle, molecular dynamics (MD) simulations, rheology
Micellar structures have been proposed for potential application in hydrotropy, biomimetics, dispersion and emulsification, enhanced oil recovery, detergency, templating, drug delivery, personal care products, drag reduction, nanoscale reaction vessels, therapeutic gene delivery, bio-catalysis and so on. Though several studies exist, there still remains a gap in the current knowledge on structural response of single micelles in solution to uniaxial extensional flow deformation. These knowledge gaps are possibly due to the inability of traditional experimental studies to investigate micellar properties at the time- and length-scale pertinent to self-assembly and micellar dynamics. To this end, this work aims to utilise coarse-grained molecular dynamics simulations to investigate the dynamics and structural response of various infinitely dilute micellar solutions under the influence of uniaxial extensional flow.
Spherical vesicles formed from hexacosanoate anion and octyltrimethylammonium cation; rod-like and worm-like micelles formed from hexacosanoate and palmitate anions; and branched worm-like micelles formed from cetyltrimethylammonium cation and sodium salicylate anion have been parametrised according to the Martini force field formalism. These structures were simulated in equilibrium; under uniaxial extensional flow; and in cessation of uniaxialextensional flow. Changes in micellar structure in uniaxial extensional flow and subsequent stress responses are presented for each micellar system at varying deformation rates. It is observed that structural changes and stress response are dependent on micellar stress relaxation ability whilst undergoing uniaxial deformation. The nature and varying influence of stress relaxation as a function of deformation rate is studied for each structure. Deformation of these structures in a direction normal to their principal orientation is also investigated. It is shown that orientation has a short-term effect on the dynamics and structural evolution of non-isotropic micellar structures. Finally, structural and stress responses following cessation of uniaxial extensional flow are presented.
Okoroafor, Kelechi, "MOLECULAR DYNAMICS STUDY ON THE STRUCTURE, DYNAMICS AND STRESS RESPONSE OF DILUTE MICELLAR SYSTEMS IN UNIAXIAL EXTENSIONAL DEFORMATION" (2018). Dissertations - ALL. 929.