films formed above the plateau are not thermodynamically stable and relax within minutes down

to the plateau surface pressure of 24 mN/m, which can be also seen as the equilibrium spreading

pressure of the PtBA blocks. Compression-expansion hysteresis experiments (3 cycles) were also

carried out in this high surface pressure region, and an example for a target pressure of 40 mN/m

is shown in Figure 3-6. The results are essentially similar to the hysteresis experiments carried

out in the middle of the plateau, with the compression curves overlapping each other, and the

expansion curves exhibiting a drop in pressure that corresponds to the slow readsorption of the

collapsed PtBA chains. AFM imaging of the LB films transferred during the second compression

at a surface pressure of 20 mN/m also confirmed here the presence of circular surface micelles

only. The morphology of the LB film transferred at 40 mN/m is shown in Figures 3-3g and 3-3h,

and aggregated domains in addition to the circular surface micelles are observed similarly as

within the plateau. Nevertheless, the transfer ratio was in this case significantly smaller than one

(~ 0.25), which indicates that the film underwent non-negligible expansion during transfer,

suggesting that the density of desorbed aggregates on the water surface is significantly greater

than as shown in Figures 3-3g and 3-3h.

 40


 35





 25


 20
 O 10 20 30
 Time (min)

Figure 3-5. Surface pressure/time isochoric relaxation plot of Dend1 after compression up to 40
 mN/m.