Chemistry, lithography and characterisation of polymer brush interfaces

This thesis examines the fabrication of heterogeneous polymer brush surfaces and the
characterisation of the interfaces present within a polymer brush. A methodology was
developed to enable modification of the bromide chain ends to form amine groups on polymer
brushes prepared by a grafting-from technique. The chemistry was tested by proof of concept
reactions carried out on silane films and on brush surfaces. The chain end modification and
photocleavable functional groups were incorporated into methodologies developed for the
formation of multiple polymer brush surfaces. Two routes were demonstrated, one using a
photocleavable silane film and the second using the attachment of photocleavable functional
groups to the amine modified brush chain ends. The formation of heterogeneous brush
surfaces through selective deprotection and multiple polymer growth has shown the ability to
control the surface chemistry with the potential for bespoke pattern formation by light
directed lithography.

Despite being able to conduct chemistry and lithography at the chain ends of polymer brushes,
the depth profile of polymer brushes has been mainly considered through classical definitions.
To investigate whether brush-liquid interfaces are well-defined, an AFM cantilever
methodology was developed to measure the resonant behaviour using the thermal noise of
the cantilever during a controlled approach-retract of the cantilever with a maximum applied
force. Through sectioned analysis of the cantilever deflection, the depth profiling of fitting
parameters for the observed resonances allowed identification of the interfaces present. By
application of the Brownian fluctuation analysis during force spectroscopy on a variety of
different polymer brush surfaces and a variety of environmental conditions, a range of
behaviours was shown to exist for these different situations. The range of behaviours
extended from an effectively solid interface at tip-brush contact to fluidic behaviour with no
well defined interface found up to the maximum applied force.