| This thesis was created as the result of studying the nanofiltration of linear polystyrene molecules of different molecular weights dissolved in a dilute regime in the theta-solvent cyclohexane through ceramic membrane disks at different temperatures to gain insight into the molecular mechanisms which can affect the process. Early in the work it was determined that separation data was not immediately forthcoming and membranes were not retaining polymer chains of molecular weights larger than the manufacturer specified cutoff limit, but that the resistance to transport across the membrane had increased. This work details the theory and practice of determining the source of the increase in resistance and speculates upon the reasons which cause current theories describing filtration processes to fail for similar systems in which the size of the solute approaches that of the pore in the nano-scale. By measuring the resistance to transport across the membranes under varying conditions, the magnitude of these interactions is examined and related to theory describing the system. By examining the filtration of 1 and 4 kilodalton polystyrene molecules dissolved in the theta-solvent cyclohexane through titania nanoporous membranes at temperatures above and below the theta-temperature it was found that polymer adsorption to the membrane surface due to dispersive Van der Waals interactions was the primary source of resistance, and the extent of this resistance was modulated by polymer-solvent philicity through affecting the polymers conformation. |
