Chemistry Reference
In-Depth Information
Fig. 1.2
Steric arrangement in macromolecules (R
ΒΌ
phenyl). (
a
) Isotactic polymer, (
b
) syndiotactic polymer (
c
)
erythrodiisotactic polymer, and (
d
) threodiisotactic polymer
a
b
H
H
H
H
H
H
H '
H '
H
R'
H '
H '
HRHR
H
R
RH
RHRH
H
H
H
H
H
H
c
d
H
H '
H
HH
R
H
H
H
HH
HH
R
R'
R
H
R'
R'
H
H
H
H
H
H
R
H
H
H
H
R
R'
R
R'
Fig. 1.3
Tritactic polymers. (
a
)
Trans-erythro
tritactic polymer, (
b
)
trans-threo
tritactic polymer, (
c
)
cis-erythro
tritactic polymer, and (
d
)
cis-threo
tritactic polymer
Several rules that govern the configuration of repeat units along the polymeric chains were
elucidated by Natta and Carradini [
24
]. A basic assumption is used to predict the lowest energy
conformation. This assumption is known as the
equivalence postulate
. It says that all the structural
units along the chain are geometrically equivalent with regard to the axis of the chain. All stereoreg-
