W. Richard Bowen and Nidal Hilal 4

232 8. ATOMIC FORCE MICROSCOPy ANd POLyMERS ON SURFACES
1000 nm
500 nm
0 nm 0 nm
500 nm
34.56 nm
1000 nm
FIgurE 8.5 AFM 3D-graph topography image of a gold substrate immersed in a toluene
solution of PS-SH (concentration: 2 mg ml –1 , molecular weight: 258 000 g mol –1 ) for 48 h.
The AFM imaging was conducted in water, which is a bad solvent for PS. The polymer
chains form aggregates (pinned micelles) on the gold terraces.
1000 nm
500 nm
0 nm 0 nm
500 nm
29.25 nm
1000 nm
FIgurE 8.6 AFM 3D-graph topography image of a gold substrate immersed in a toluene
solution of PS-SH (concentration: 2 mg ml –1 , molecular weight: 51 500 g mol –1 ) for 48 h.
The AFM imaging was conducted in water, which is a bad solvent for PS. The polymer
chains form aggregates (pinned micelles) on the gold terraces.
micrometre area. The globular islands are too many and too large in size
to be individual collapsed chains.
Since for sufficiently long incubation time we expect to be close and
above the overlap grafting density, the polymer chains are too close with
each other to collapse separately. Instead, they collapse fusing together in
small clusters, the size of which is moderated by the grafted tethers. They
form aggregates connected to the surface through the tethers; these structures
have been called ‘pinned micelles’ or ‘octopus surface micelles’ and
they have been predicted by theory [21, 22].