,5.0 *n


 2) Trannsfer at
 gI 2 mN/mr

 Tr~ns~ferred at "Transerred atl
 ar = mNrini 3E = mN/m










Figure 5-23. AFM topographic images and corresponding cross-sections of the (PB(Si(OEt)3)-b-
 PEO)3 Star block copolymer LB films cross-linked at 9 mN/m (pH = 3.0, t = 10 h) and
 transferred at 9 and 2 mN/m. The images are 2 x 2 ;m2

 A final experiment was designed to prove that, when the cross-linking reaction is carried

out above 10 mN/m, the PEO chains are irreversibly dissolved and held into the aqueous

subphase, underneath the cross-linked PB network. After cross-linking the monolayer at 20

mN/m (t = 10 h, pH = 3.0), the barriers were fully expanded and the isotherm of the cross-linked

monolayer was recorded as shown in Figure 5-24 (blue curve). The PEO-related phase transition

(pseudoplateau) is no longer present, which confirmed that the PEO chains could not readsorb at

the interface during monolayer expansion. A control experiment was carried out by recording the

isotherm of a monolayer cross-linked below the surface pressure corresponding to the PEO

aqueous dissolution (5 mN/m, Figure 5-24, red curve). As expected, the PEO pseudoplateau is

still present (even after several compression-expansion hysteresis cycles), which confirms that it

is possible at high surface pressure (7<> 10 mN/m) to freeze the "bilayer" conformation of the

cross-linked material consisting of a cross-linked PB layer covalently attached to a PEO

sublayer.