Chemistry Reference
In-Depth Information
can be calculated
a priori
[5]
. For whole polymers, all species elute effectively at
zero
c
and
V
5
4
π½η
M
=μ
(3-99)
L
(instead of the
numerical value given in
[20]
) in order to coincide with
Eq. (3-64)
. This proce-
dure is necessary for high-molecular-weight polymer standards in good solvents.
In other cases, the hydrodynamic volume calibration is equivalent to the infinite
dilute [
The constant
μ
in
Eqs. (3-98) and (3-99)
must equal 10
π
]
M
method. With this modification, the calibration curve for narrow dis-
tribution standards is converted to the form shown in
Fig. 3.12
, using
Eq. (3-98)
to translate
M
to hydrodynamic volume
V
. The curve is then applied to analysis
of whole polymers through the use of
Eq. (3-99)
.
When MHS constants for a particular polymer are not known, they can be esti-
mated from GPC chromatograms and other data on whole polymers of the partic-
ular type
[21]
. It is not necessary to use fractionated samples in this method of
determining
K
and
a
.
A parameter
J
is defined as the product of intrinsic viscosity and molecular
weight of a monodisperse species
i
. That is,
η
J
i
½η
i
M
i
(3-100)
With
Eq. (3-95)
,
J
aða1
1
Þ
i
K
1
=ða1
1
Þ
½η
i
5
(3-101)
- 44
- 42
- 40
- 38
- 36
- 34
130
140
Elution volume (mL)
150
160
FIGURE 3.12
Universal Calibration Curve in terms of Hydrodynamic Volume V and Elution Volume.
