compression-expansion cycles essentially overlapped the second cycle with no noticeable

pressure changes concerning the collapse or the expansion pseudoplateau.

 25


 20
 SFirst compression
 I ci First expansion
 S15 .o Second and third compressions
 Z Second and third expansions

 S10







 0 200 400 600 800
 MMA (lj)

Figure 4-7. Compression-expansion hysteresis plot of PCL1250.

 Typical AFM images of the PCL homopolymers LB films transferred below monolayer

collapse (7<= 7 mN/m), before crystallization on the water surface takes place, are shown in

Figure 4-8a and 4-8d. Surprisingly, PCL crystals could be observed. According to the isotherms

that are characteristic of liquid condensed phases in this low surface pressure range, the PCL

homopolymers are transferred into smooth and hydrated monolayers adsorbed onto the mica

surface. We believe that upon drying, during and after transfer, part of the PCL chains leave the

surface and crystallize, which likely results in a mica surface only partially covered with

adsorbed or crystallized PCL chains. For comparison, PCL homopolymers were also transferred

beyond monolayer collapse, after crystallization on the water surface takes place (Figure 4-8b, 4-

8c, and 4-8e). The transfer ratios were in this case significantly greater than 1 (~ 2-3), which was

predictable since crystallization and therefore intrinsic MMA decrease take place over time in