upon barrier expansion. AFM imaging of the LB films transferred during the second

compression at a surface pressure of 20 mN/m confirmed the presence of adsorbed and circular

surface micelles and the absence of collapsed domains. Nevertheless, a drop in pressure is

observed during barrier expansion. Faster barrier speeds increased the pressure drop, which

suggests that the readsorption kinetics of the collapsed PtBA segments are slower than the barrier

expansion speed.

 30

 Compression

 20 -2
 Expansion






 O 25000 50000 75000 100000
 MMA (A2

Figure 3-4. Compression-expansion hysteresis plot of Dend1 (target MMA = 20,000 A+2.

 Further compression in the low MMA region leads to a sharp surface pressure increase.

The films formed in this region of the isotherm should be unstable since the surface pressure is

higher than the PtBA collapse pressure of 24 mN/m. This was checked by carrying out isochoric

experiments. A typical isochore after compression up to 40 mN/m is shown in Figure 3-5. The

surface pressure undergoes a sudden drop within the first seconds of the experiment before

leveling off after a few minutes around 24 mN/m. It is not clear to us whether the sharp surface

pressure increase upon high compression in the isotherm originates from interactions between

the collapsed and desorbed aggregates formed in the plateau region or between eventual

remaining adsorbed PtBA segments. In any case, the isochoric experiments confirmed that the