2 nm


 11nm 10 ~ nm e e
 0 nm m 0nm



Figure 3-8. Topographic AFM images of PAA250K LB films transferred at 1.5 (a), 3 (b), and 3.5
 mN/m (c).

 The spreading solutions of Dend2 were prepared by using the same solvent mixture as for

PAA250K (chloroform/ethanol mixture, 1/2 in volume). Similarly as for PAA250K, HO stable

Langmuir monolayers could be formed for Dend2 under basic conditions with its irreversible

dissolution in the aqueous subphase. Contrary to the other PS-b-PAA systems reported in the

previous literature,20,98,99 the PS wt % in Dend2 is too low to allow it to act as an anchor and thus

preventing the dendrimer-like aqueous dissolution. Nevertheless, under acidic conditions (pH =

2.5), the PAA segments of Dend2 are now protonated, and, similarly as for PAA250K, Dend2

becomes surface active. The resulting isotherm is shown in Figure 3-9, and the inset shows the

monolayer compressibility plot (K, Equation 3-2) versus surface pressure.96

 1 1 d (NLVA )
 K= (3-2)
 E, MVIA d(Fir)

In the high MMA region, the surface pressure slowly increases before reaching a pseudoplateau

around 5 mN/m (maximum in monolayer compressibility as seen in the inset of Figure 3-9) and

sharply increasing under high compression up to approximately 10 mN/m. A pseudoplateau was

already observed in the previous literature by Currie et al. only for long PAA chains in linear PS-

b-PAA systems under acidic conditions, where they demonstrated by surface pressure and

ellipsometry measurements the presence of a pancake-to-brush transition in the pseudoplateau