Polymer brushes on charged surfaces : synthesis, characterisation and interactions

• Main Author: Snow, John Francis Timothy Barter
• Published: University of Bristol 2015
• Subjects: 547
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686190

Polymer brushes anchored to surfaces offer an effective route to modification of interfacial properties such as propensity to fouling , friction mediation and wetting. However, direct physical measurements of such systems, facilitating the refinement of polymer brush growth and comparison against polymer brush theories, remain limited despite considerable research efforts in this area. This thesis describes an investigation on normal and lateral forces between surfaces bearing a polY(2-(methacryloyloxy)ethyl}dimethyl-(3-sulfopropyl)ammonium hydroxide), P(SBMA), brush grafted from a novel two dimensional cationic macroinitiator using a surface force apparatus, SFA. Preceding such results this thesis first details the design principles, synthesis and characterisation of a two dimensional cationic macroinitiator facilitating the grafting of polymers from mica and silicon substrates. From this, several polymers were successfully grafted on both mica and silicon. Normal force measurements are then reported in an aqueous environment as well as Na(N03) and Ca(N03)2 salt solutions in addition to solutions composed of water and an ionic liquid, l-hexyl-3-methylimidazolium chloride. These results show the presence of salts altering brush swelling and solvent tenacity, manifesting as changes in measured brush thickness and the force required to deform such a brush layer. Observation of friction mediated by the polymer brush systems was also made with sliding as well as stick-slip behaviours seen for P(SBMA) systems in Ca(N03)2 salt solutions. Finally, the thermal response for ethylene glycol methyl ether methacrylate polymer brushes anchored to polystyrene particles was investigated. Results gathered for this system show that the presence of a dynamic monomer density along the length of a polymer chain gave rise to a complex interplay of forces. This complex relationship exhibited a marked difference in brush response compared to similar systems grafted from flat surfaces.