The effect of specifically interacting functional groups (sticky foot) located at the chain ends of polystyrene on the adsorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid end-groups (PS-OH, PS-COOH, HO-PS-OH and HOOC-PS-COOH) in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC) is developed as an analytical technique to predict trends in the adsorption of the polymers in a range of solvents. In particular the information about the location of the end-group and therefore different chain architectures at the interface are inferred from this simple technique. Adsorption isotherms are obtained for each of the functionalized polymers of four different molecular weights, the selection of which was based on the TLC results. Kinetics of adsorption and the adsorbance data are determined by liquid scintillation counting of tritium labelled polymers. Graft density and surface excess data are calculated from the adsorbance data and other known parameters. It is shown, from these data, that polystyrenes with a carboxylic acid end-group form weakly stretched brushes at the glass-cyclohexane interface and mushrooms at the glass-toluene interface a result consistent with the higher osmotic repulsions towards packing in good solvents. Polystyrenes with functional groups at both the chain ends are hypothesized to form a range of structures from those dominated by tails at higher concentrations to those dominated by loops (in a good solvent) and trains (in a theta solvent) at lower solution concentrations. At higher molecular weights it is shown that functionalized polystyrenes behave as though they are not functionalized a result consistent with the TLC predictions. Hydroxyl end-group is shown to be an ineffective sticky foot from its adsorbance vis-a-vis polystyrene. The segment density distribution away from a polished silicon surface for a carboxylic acid end-functionalized polystyrene adsorbed from cyclohexane is determined by neutron reflection technique. The dry film thicknesses of polymer modified glass surfaces are determined by x-ray photoelectron spectroscopy. It is shown from the water contact angle data that a highly hrdrophilic surface of glass is converted to a completely hydrophobic surface by the adsorption of the functionalized polystyrenes. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8377 |
| Date | 01 January 1992 |
| Creators | Iyengar, Dhamodharan R |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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