Biomedical Engineering Reference
In-Depth Information
Fig. 27
Π
-
Γ
isotherms (
a
)and
ε
-
Γ
for sample I (PEO-PPO-PEO) on the air/water
interface at various temperatures; 9
◦
C(
Γ
∗
indicates the sur-
face mass density where the static elasticity at 9
◦
C reaches the maximum, not the onset
point of semi-dilute solution
), 23
◦
C, (
)and30
◦
C(
•
).
of 17
A
2
/monomer and
m
2
correspond-
ing to
A
nominal
of 14A
2
/monomer. The conformational change with changing
area per monomer may be possible, but
A
nominal
at higher temperature is
even smaller than in the non-hydrated area, 20A
2
/monomer; and recent ex-
perimental data [125] suggested that the PEO blocks form brushes under the
surface at higher concentration, which is consistent with our previous argu-
ment [127] that some of the end-chain PEO blocks penetrate into the subphase.
We turn to the results obtained with sample II, 10R5 (PPO-PEO-PPO).
In Fig. 28 are shown the results for this sample: (a)
Γ
∗
at 23 and 30
◦
Careabout0.5 mg
/
Π
-
Γ
isotherms and (b)
the static surface elasticity
ε
s
as a function of
Γ
at three different tempera-
Γ
∗
(equaling
tures. Relative to
Π
-
Γ
isotherms and the surface concentration
cm
2
)when
0.4 mg
ε
s,max
, there is no temperature dependence
which is in complete contrast to those for sample I; no temperature de-
pendence can be discerned within experimental uncertainties in this case.
/
ε
s
reaches
