Chemistry Reference
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data also provided an additional verification of film thickness. The dielectric con-
stant,
ε,
was obtained from the refractive index, n, through the Maxwell relation:
= n
2
ε
3. RESULTS AND DISCUSSION
3.1. Solution properties and thermal analysis
High molecular weight materials were obtained as evidenced by their solution
viscosities, η, in MSA, listed in Table 1 and by the tenacity of the films fabri-
cated. Moisture uptake for the fluorine containing polymers was less than 0.2%.
Solvents for the polymers ranged from chloroform and tetrahydrofuran (THF) for
the highly fluorinated polymers to o-dichlorobenzene and MSA for the polymers
with a high content of the aromatic hydroxyl pendants. The T
g
s of the polymers,
determined by differential scanning calorimetry (DSC), are listed in Table 1,
which also lists T
g
values for selected samples from dynamic mechanical analysis
(DMA). The values from the two different methods are in substantial agreement.
A typical example of DSC data obtained on sample
6
is shown in Figure 1. The T
g
value (361
C) is obtained from the inflection point (I).
The introduction of intramolecular hydrogen bonding via the interaction of
pendant hydroxyl groups with the C=N of the benzoxazole unit greatly enhances
°
Table 1.
Solution and thermal properties of various fluorinated benzoxazole homo- and copolymers with hy-
droxyl pendants
[η]
a
T
g
b
(°C)
T
g
c
(°C)
Polymer number
A
B
X
Y
1
-H
-H
0
100
2.30
325
315
-H
-H
50
50
1.37
346
336
2
3
-OH
-H
100
0
2.06
426
390
4
-OH
-H
90
10
1.30
415
410
-OH
-H
70
30
2.34
373
371
5
6
-OH
-H
50
50
1.35
362
353
7
-OH
-OH
100
0
3.10
>450
454
-OH
-OH
75
25
1.34
>450
-
8
9
-OH
-OH
50
50
0.88
>450
430
10
-OH
-OH
25
75
0.47
>450
-
a
MSA, 30°C, 0.12 g/dL
b
DSC data
c
DMA, loss tangent peak
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