Some recent and ongoing projects
- We are studying the wetting of
surfaces by simple and by polymeric liquids. Several issues are investigated.
One important basic question is whether non-wetting films break up and dewet
via nucleated hole formation, or whether they rupture via capillary wave amplification
for thin enough films. Another relates to the modification of the wettability
of surfaces by attached polymers or by different surface treatments (e.g.
radiation cross-linking); we study the wetting behaviour of polymer surfaces
by simple liquids or by the polymers themselves (including the so-called autophobicity
effect) (related publications).
- Finite size effects in thin
polymer films can occur when the thickness of the films is of the order of
the polymer dimensions. We examine the way in which the interface between
coexisting polymer phases in a thin film varies with the film thickness, and
the effect of film thickness on the surface-segregation from a polymer mixture
(related publications).
- Development and extension of
the nuclear reaction analysis (NRA) method
to determine composition-depth profiles at nanometre spatial resolutions (related
publications).
- Composition-depth profiling
of polymer mixtures to investigate their thermodynamic and transport properties,
and to examine different theoretical models for surface segregation and wetting
from such mixtures (related publications).
- The effect of adsorbed and grafted
polymers on normal interactions between surfaces, and examining experimental
results in the light of recent models (related publications).
- Several projects make use of
the surface force balance (SFB) to determine normal and especially frictional
(shear) forces between surfaces that approach or slide past each other. Studies
on the effect of surface-attached flexible polymers - both adsorbed and grafted
- on these forces are currently in progress, as well as on more rigid molecules
such as liquid crystals, which may have interesting anisotropic behaviour.
We are also extending this work to the case of charged polymers, with relevance
to the mechanism of biolubrication in mammalian joints, and to the direct
measurement of specific interactions between chemical groups (related
publications).
- Friction and lubication by simple
molecules, and particularly the question of how a liquid that is confined
to progressively thinner films reverts to being solid-like when it is only
a few molecular layers thick. The stick-slip behaviour of such solidified
liquids is directly related to their function as lubricants, and is being
studied in detail (related publications).
- Development and extension of
the surface force balance to increased sensitivity
and resolution, to enable direct measurements of specific molecular interactions
between reacting chemical groups (related publications).
