Biomedical Engineering Reference
In-Depth Information
approached from the two-phase side upon compression, which leads to an
increase in TLI, but produces roughly the same result, with no significant
hysteresis. The solution is allowed to equilibrate in the one-phase region at a
much higher pressure than the expected CP for 15 min before a new data point
is taken. For all data points, the TLI results are stored and analyzed as a
function of temperature, pressure, and time.
Since the SLI and hydrodynamic radius increase sharply at the MP, micelle
formation can be measured using high-pressure dynamic light scattering. For
these measurements, the high-pressure cell is coupled with an Ar
+
ion laser
(National Laser, model 800BL) operating at a l 5 488 nm wavelength with a
Brookhaven BI-9000AT correlator. The coherence area is controlled by a
pinhole placed before the detector. The laser and detector are linked to the high-
pressure cell by optical fibers produced by Thorlabs. The high-pressure optical
interface design is different from, but inspired by, the approach described by
Koga et al.
3
The scattered-light intensity is recorded and measured for
isothermal measurements upon increasing or decreasing pressures at a rate of
30-60 bar min
21
. More detailed descriptions are available elsewhere.
13-15
d
n
4
y
3
n
g
|
1
Figure 13.3
Transmitted light intensity plot of PEG-b-PCL (5k-b-11k) in 33%
trifluoromethane and 67% dimethyl ether at 40 uC and 1 wt%.
