Biomedical Engineering Reference
In-Depth Information
Fig. 11.6
Simulated LC chromatogram for a copolymer PC- Nylon 6 obtained by melt-mixing at
t
D
3
min (
a
), At
t
D
8
min (
b
)
the type
mL, and that the resolving
power is almost infinite. As a result, the two homopolymers elute almost exactly
at
V
e
D g
0
C g
1
r
A
, with
g
0
D 1
mL and
g
1
D 2
mL, with very small spreads around these values. On the
other hand, the peak due to copolymer chains is centered around
V
e
D 1
mL and
V
e
D 3
mL and it
is very broad. Actually, it is so broad that it superposes with Z1 and Z2. This consti-
tutes a small obstacle that can be easily circumvented using a deconvolution process
to estimate Z1 and Z2. The simulation clearly indicates that homopolymer chains
disappear at early stages of the exchange reaction.
V
e
D 2
11.8
The Sequence of Copolymer Fractions
Copolymer fractions are usually collected at the exit of a liquid chromatographic
device. There are several techniques that yield copolymer fractions. For instance,
precipitation fractionation, extraction fractionation (using a simple SOXHLET ex-
tractor), gradient elution fractionation, field flow fractionation (FFF), supercritical
CO
2
fractionation, and temperature-rise-elution fractionation (TREF) [
32
]. The
composition (molar fraction of A units) of the
m
th fraction and of the unfractionated
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