Organisation and dynamics of an amphiphilic block copolymer at the air/water interface

Abstract

This thesis describes the techniques of anionic polymerisation and characterisation used in the synthesis of poly(methyl methacrylate)/poly(ethylene oxide) diblock copolymers, the various surface techniques used to examine the interfacial properties of these copolymers spread on water, and the dynamics of these copolymers in solution. The surface techniques used were surface pressure-concentration isotherm studies, neutron reflectivity, surface quasi-elastic light scattering, and ellipsometry. The thermodynamics of micellization and dynamic properties of the copolymer solutions were investigated using light scattering. The diblock copolymers had a target composition of 50:50 mole ratio and M(_W) = 50000. In addition, several copolymers had one or both blocks holly deuterated which was necessary for the neutron reflectivity studies where contrast variation was required to apply the kinematic approximation. Surface pressure isotherms give thermodynamic information about the behaviour of polymer segments at the interface. It has been possible to interpret this behaviour by using neutron reflectivity to obtain information concerning die thickness and distribution of the PMMA and PEO blocks, and water at the interface. The trends in layer thickness have been supported by the ellipsometric measurements and interpretation of the viscoelastic SQELS data has allowed conclusions about the hydrodynamics of the polymer chains at various surface concentrations.