Biology Reference
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In Fig. 5.1a, the solid lines are fits to the experimentally observed
chemical shifts using
= 52. Moreover, the distribution of various
self-assembled oligomers is given in Fig. 5.1b as a function of the
[
K
4
M), most PDI monomers remain as
free molecules and the monomer population is at least two orders of
magnitude higher than the dimer population. At high concentration
region (>0.1 M), various self-assembled oligomer concentrations
rise rapidly.
A
]. At low concentration (<10
0
8.8
(a)
10 -3
(b)
[A]
8.6
10 -5
Ha
10 -7
[A:A]
Hb
8.4
10 -9
[A:A:A]
10 -11
8.2
[A:A:A:A]
10 -13
8.0
10 -15
[A:A:A:A:A]
10 -17
7.8
10 -4
10 -3
10 -2
10 -1
10 -4 10 -3 10 -2 10 -1
Initial Concentration [A o ]
Concentration (M)
Figure 5.1
(a) Observed (circles) and theoretical (solid line, Eq. 5.2)
chemical shifts for
aromatic protons Ha (next to diimide)
and Hb (at bay position). (b) Theoretical prediction of
various self-assembled oligomers of
1A
1A
as a function of
initial concentration [
A
].
0
depends on the
solvent used. Good solvents such as chloroform will solvate the
compound (solvent molecules surround the solute molecule) and
therefore have relatively low association constants. Conversely,
poor solvents such as methanol will promote self-association and
therefore yield large formation constants. The self-association
constant
Generally, the self-association constant
K
SA
1
indicates that the formation of self-assembled
oligomers is spontaneous at a reasonable concentration. To validate
these results, variable temperature
K
= 52 M
SA
1
H NMR of the PDI monomer
2
D]) was carried out. Again, large
upfield chemical shifts (Fig. 5.2a) were observed as temperature was
lowered, indicating favorable
in CD
Cl
(
K
[CD
Cl
]
K
[CCl
2
SA
2
2
SA
3
π−π
stacking at low temperatures. Self-
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