Polyimides based on rhenium(I) diimine complexes - Polyimides and Other High Temperature Polymers - page 91

Figure 2. Synthesis of polyimide with rhenium diimine complexes.

2.2. Physical measurements
The polymer film (thickness = 0.6 to 1.0 µm) for photocurrent measurement was
prepared by casting a polyimide solution in NMP on an indium-tin-oxide glass
slide. A layer of aluminium electrode (10 nm) was deposited on the film surface
by thermal evaporation. A Laser Physics Ar-ion laser (488 and 514 nm) was used
as the light source. The incident laser light beam was modulated with a mechani-
cal chopper and the photocurrent was measured with a Stanford Research System
SR 510 lock-in amplifier.

3. RESULTS AND DISCUSSION

The TGA thermogram of is shown in Figure 3. Two major weight

losses at ca. 250 and 550°C were observed in the TGA thermogram. We suggest
that the first process accounts for approximately 20% of weight loss and is proba-
bly due to the decomposition of the rhenium carbonyl moiety, while the second
weight loss corresponds to the degradation of the polyimide main chain. The
structure of the polyimide was confirmed by FTIR spectroscopy. Three very
strong stretching bands corresponding to the characteristic C

Re-6FDA

O stretching of the
facial metal carbonyl ligands are observed at 2020, 1972 and 1914 cm -1 . In addi-
tion, other absorption bands at 1603 and 830 cm -1 are also observed, which are
due to the diimine C=N stretching and the out-of-plane bending of the 1,4-
disubstituted benzene, respectively. Other stretching bands observed at 1780,
1720, 1372 and 725 cm -1 are assigned to the C=O stretching, C-N stretching and

≡