W. Richard Bowen and Nidal Hilal 4

240 8. ATOMIC FORCE MICROSCOPy ANd POLyMERS ON SURFACES
Y Range: 1.21 μm
–0.313
–0.918
–1.52
Height range: 7.591 nm
0.634 1.24 1.84
X Range: 1.21 μm
FIgurE 8.13 AFM topography image of an 18-arm star polymer adsorbed on mica,
incubation time of 20 min.
not interpenetrate. The large number of arms and the resulting crowding
effect and increased osmotic pressure within their volume did not permit
interpenetration between the star polymers and they continued to collapse
individually despite the high adsorbed amount. This is a further
manifestation of colloidal behaviour.
8.6 ConCLuSIonS
We have provided several examples of the use of AFM in investigations
of the fine structure and local nanomechanical properties of polymer
monolayers and submonolayers. AFM is ideally suited to study the lateral
inhomogeneities of such ultrathin coatings and their non-linear compliance
and adhesion either in dry state or within liquid environment.
Although the time resolution of the (classical) AFM imaging modes (tapping
mode in particular) is not particularly high, the molecular kinetics
of polymers on surfaces can be sluggish enough to allow the real-time/
real-space monitoring of various physico-chemical surface processes. As
miniaturisation of electronic and medical devices is rapidly approaching
the nanometre scale, the AFM is gradually becoming the most important
characterisation tool of nanostructural and nanomechanical properties.
Beyond the unique characterisation capabilities, systematic AFM studies
on model systems can ultimately lead to a formulation of design criteria
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