in the mixed monolayers, as shown by the shift of the compressibility maximum toward higher

surface pressures (inset of Figure 4-22). This is a first indication that PEO2670 and PCL2000

are miscible when both blocks are adsorbed at the A/W interface."s Figure 4-24 shows plots of

MMA versus the mole fraction of PCL2000 for three surface pressures below 6.5 mN/m (2, 3,

and 4 mN/m). The data exhibit negative deviations from ideal mixing (dashed lines), which

confirms that in the surface pressure range where they are adsorbed at the A/W interface (7<< 6.5

mN/m), PCL2000 and PEO2670 do not phase-separate and thermodynamically interpenetrate

each other.151,152 From these results, we can reasonably extrapolate that the PEO and PCL

segments of the linear diblock copolymers are miscible as well below 6.5 mN/m, and therefore

that their A/W interfacial adsorption probably does not lead to the formation of surface micelles

previously observed for other amphiphilic block copolymers.97,153,154 These results are in good

agreement with a previous study that demonstrated the miscibility of PEO and PCL

homopolymers in the amorphous phase in blend films prepared by solution casting.'


 S2000
 <(~ As = 2 m Nlm
 = 3 mNlm
 Q) I a = 4 mNlm







 S600
 2 0 0.2 0.4 0.6 0.8 1
 PCL2000 mole fraction

Figure 4-24. MMA plots versus mole fraction of PCL2000. Dashed lines: theoretical ideal
 mixing.