| This thesis focuses on the effect of interfaces on the properties of “soft” materials such as an isotropic droplet in the presence of an external field, a freely suspended nematic liquid crystal droplet, a liquid bridge in the presence of a static or dynamic gravitational field and the diffusion of organic materials into polymers. We have used either numerical or molecular dynamics simulation techniques to understand the effect of interfaces in each of the above cases.; A drop of fluid which is initially held spherical by surface tension will deform when an external field is applied. A numerical technique is presented to solve this problem. The results show that when the dielectric constant K is larger than a critical value Kc and the field strength E is larger than EC, the drop develops conical tips at its ends. For K < Kc, however, the drop elongates and retains its original nearly prolate spheroidal shape and shows growing deviations from a prolate spheroid without developing conical tips as we increase the field.; The evolution of axisymetric liquid bridges subjected to static and oscillatory forces has been also studied numerically. The analysis has been performed using a one-dimensional system of nonlinear equations. Theoretical results are compared with experiment and the agreement is found to be satisfactory.; The effect of interfaces on liquid crystal droplets has been one of the main focuses in the liquid crystal community. We have used atomistic molecular dynamics simulations to model the detailed molecular configuration of 5CB (4-n-pentyl-4′-cyanobiphenyl) molecules in the form of a nanoscopic liquid crystal droplet in a vacuum microgravity environment. We find the equilibrium state of droplets consisting of as few as 26 or 50 molecules to exhibit significant nematic ordering.; We can also have internal surfaces in many different cases, and the diffusion of organic materials into polymers is one of them. The diffusion of solvents into polymers often causes swelling, and may lead the polymer to pass from the glassy to the rubbery state. However, this process is extremely slow and poorly understood on a molecular level. We show that it is the presence of partial charges on the solvent material that mainly controls the speed of the diffusion process. By removing the partial charges on the methanol atoms we are able to obtain useful information about the processes of swelling and plasticization due to the diffusion of methanol into poly(methyl methacrylate) in a reasonable computational time. |
