copolymers such as spherulitic, dendritic, and needlelike structures, with the presence of the PEO

core strongly influencing the crystallization of the PCL blocks. The linear diblock copolymers

successfully self-assembled as well at the A/W interface to form stable Langmuir monolayers.

Preliminary investigation on PEO2670 and PCL2000 homopolymers blends showed that these

polymers are non-ideally miscible for low surface pressures when both blocks are adsorbed at the

A/W interface. Nevertheless, the individual collapse surface pressures (PEO2670 aqueous

dissolution around 6.5 mN/m and PCL2000 crystallization above the interface around 13 mN/m)

were not significantly influenced by the presence of the other homopolymer. For the linear PEO-

b-PCL diblock copolymers, an additional PEO phase transition at 10.5 mN/m was observed

corresponding to the formation of a PEO brush underneath the anchoring PCL segments. These

two PEO phase transitions were not observed for the star-shaped PEO-b-PCL block copolymers,

and our investigations consequently confirmed the significant influence of the polymer

architecture on its interfacial properties. AFM imaging of the linear PEO-b-PCL diblock

copolymers LB fi1ms for high surface pressures confirmed the formation of PCL crystals with

hairlike/needlelike architectures. These crystals were significantly different from those obtained

in LB films of PCL homopolymers, confirming the strong influence of the PEO block on the

crystallization of the PCL segments. This fundamental investigation gave interesting insight on

the interfacial self-assembly of PEO-b-PCL copolymers and showed that an accurate and easy

control of the conformations and the orientations of the different blocks at the A/W interface can

be easily achieved by simply varying the polymer architecture or the surface pressure.

 4.4 Experimental Methods

4.4.1 Langmuir Films

 Surface pressure measurements were accomplished by use of a Teflon Langmuir trough

system (W= 160 mm, L = 650 mm; KSV Ltd., Finland) equipped with two moving barriers and a