Chemistry Reference
In-Depth Information
Table 2.1. Comparison of theory and experimental data of various cellulose
derivative solutions. (From Flory, 1978.)
φ
∗
(theory)
φ
∗
(experiments)
Derivative
Solvent
diacetate cellulose
acetone
0.284
0.33
dimethyl formamide
0.284
0.37
dioxane
∗∗
0.284
0.35
m-cresol
0.284
0.28
trifluoroacetic acid
0.284
0.25
ethyl cellulose
acetate
0.32
0.39
dichloroacetate
0.32
0.28
hydroxypropyl cellulose
water
0.38
0.33, 0.37, 0.30
methanol
0.38
0.33
ethanol
0.38
0.37, 0.39
acetate
0.38
0.27
dimethylacetylamide
0.38
0.32, 0.35
For ethyl cellulose, assume
ρ
=1
.
3g
/
cm
3
,
l
k
= 180 A and one obtains
x
k
= 23 and
φ
∗
=0
.
32
.
For hydroxypropyl cellulose
ρ
=1
.
2g
/
cm
3
,
l
k
= 180 A:
φ
∗
=0
.
38
.
x
k
=19
,
Table 2.1 summarizes the above calculations and compares them with
the experimental data. Good agreement was found.
2.2.6.
Discussion of the Flory theory
Equation 2.28 was suggested in Flory's 1956 approximation which is actu-
ally valid for a two-dimensional lattice. As shown in Figure 2.11,
y
is the
projection of a rod's length onto the plane (X-Y) perpendicular to the
director in a three-dimensional lattice. But one would find that the sys-
tem shows some orientational order at all concentrations even though for
isotropic phase.
To overcome the contradiction, Flory and Ronca (1979) made the
following improvement for the three-dimensional lattice
y
=
x
sin
θ
(
|
sin
φ
|
+
|
cos
φ
|
)
(2.57)
