The FTIR spectra of LPUV-irradiated TeMPD-based polyimides for 10 J/cm
2 ,
unirradiated TeMPD-based polyimides (after thermal imidization), and TeMPDbased polyamides are shown in Fig. 19. As shown in Fig. 19a, the N–H stretching
bond peak was observed near 1650 cm
À1 in DSDA-TeMPD polyamide. However,
the peak was not observed after thermal imidization. In contrast, the intensity of
the O–H stretching peak near 3300 cm
À1 decreased and that of the C=O
stretching peak near 1750 cm
À1 increased after thermal imidization. In the case
of 6FDA-TeMPD, the N-H bond peak derived from polyamide was observed
before thermal imidization as shown in Fig. 19b. For DSDA-TeMPD also, the
N-H bond peak was not observed after thermal imidization. In addition, the O–H
stretching peak intensity increased and the C=O stretching peak intensity
decreased upon LPUV irradiation. These results are consistent with those in our
previous study (Sato et al. 2011). The N-H bond peak was observed for CBDATeMPD after thermal imidization as shown in Fig. 19c. The peak intensity
slightly decreased after thermal imidization. CBDA-TeMPD was not fully
imidized. Through LPUV irradiation, the O–H stretching and N-H bond peaks
intensities increased. In contrast, the C=O stretching peak intensity slightly
decreased. These results indicate that the photoreaction mechanism of DSDATeMPD is similar to that of 6FDA-TeMPD. Therefore, an intermolecular crosslinked photoreaction owing to CT interaction occurred in DSDA-TeMPD, as
shown in our previous study (Sato et al. 2011, 2012). In contrast, the
intermolecular cross-linked photoreaction only partially occurred in CBDATeMPD polyimide.
The thermal imidization ratio can be expressed by comparing the O–H stretching
peak’s intensity, I, as follows: (I (before thermal imidization) - I (after thermal imidization) )/ I (before
thermal imidization) . The ratios of DSDA-TeMPD, 6FDA-TeMPD, and CBDA-TeMPD
were 99.7%, 96.2%, and 63.4%, respectively. CBDA-TeMPD exhibited a lower
reaction ratio than DSDA-TeMPD and 6FDA-TeMPD because of low main-chain
rigidity. The thermal imidization reaction of CBDA-TeMPD proceeds weakly. The
CBDA-TeMPD polyimide after thermal imidization contained approximately half
polyamide. The polyamide depends on the photoalignment characteristics. It is
expected that the photoalignment characteristic of CBDA-TeMPD is different from
those of DSDA-TeMPD and 6FDA-TeMPD.
The UV spectra from 2.5 to 6.5 eV of these LPUV-irradiated TeMPD-based
polyimides for 10 J/cm
2 , unirradiated TeMPD-based polyimides, and TeMPDbased polyamides are shown in Fig. 20. Strong peaks near 6.2 eV were observed
in DSDA-TeMPD and 6FDA-TeMPD. The peak position shifted to 5.5 eV after
thermal imidization, and the energy after imidization was lower than that before
imidization. In addition, the peak intensity decreased after LPUV irradiation. Moreover, weak peaks near 4.4 eV were observed in DSDA-TeMPD and 6FDA-TeMPD
before imidization. The peak position shifted to 4.0 eV after thermal imidization and
LPUV irradiation. In contrast, a strong peak near 6.0 eV was observed in CBDATeMPD before thermal imidization; the peak intensity decreased without a change in
the peak position. A weak peak near 4.5 eV was newly found after thermal
imidization and LPUV irradiation. There was no change in the intensity and position
18 Photoalignment of Liquid Crystal Molecules Using Fluorine-Containing. . .
515
2 ,
unirradiated TeMPD-based polyimides (after thermal imidization), and TeMPDbased polyamides are shown in Fig. 19. As shown in Fig. 19a, the N–H stretching
bond peak was observed near 1650 cm
À1 in DSDA-TeMPD polyamide. However,
the peak was not observed after thermal imidization. In contrast, the intensity of
the O–H stretching peak near 3300 cm
À1 decreased and that of the C=O
stretching peak near 1750 cm
À1 increased after thermal imidization. In the case
of 6FDA-TeMPD, the N-H bond peak derived from polyamide was observed
before thermal imidization as shown in Fig. 19b. For DSDA-TeMPD also, the
N-H bond peak was not observed after thermal imidization. In addition, the O–H
stretching peak intensity increased and the C=O stretching peak intensity
decreased upon LPUV irradiation. These results are consistent with those in our
previous study (Sato et al. 2011). The N-H bond peak was observed for CBDATeMPD after thermal imidization as shown in Fig. 19c. The peak intensity
slightly decreased after thermal imidization. CBDA-TeMPD was not fully
imidized. Through LPUV irradiation, the O–H stretching and N-H bond peaks
intensities increased. In contrast, the C=O stretching peak intensity slightly
decreased. These results indicate that the photoreaction mechanism of DSDATeMPD is similar to that of 6FDA-TeMPD. Therefore, an intermolecular crosslinked photoreaction owing to CT interaction occurred in DSDA-TeMPD, as
shown in our previous study (Sato et al. 2011, 2012). In contrast, the
intermolecular cross-linked photoreaction only partially occurred in CBDATeMPD polyimide.
The thermal imidization ratio can be expressed by comparing the O–H stretching
peak’s intensity, I, as follows: (I (before thermal imidization) - I (after thermal imidization) )/ I (before
thermal imidization) . The ratios of DSDA-TeMPD, 6FDA-TeMPD, and CBDA-TeMPD
were 99.7%, 96.2%, and 63.4%, respectively. CBDA-TeMPD exhibited a lower
reaction ratio than DSDA-TeMPD and 6FDA-TeMPD because of low main-chain
rigidity. The thermal imidization reaction of CBDA-TeMPD proceeds weakly. The
CBDA-TeMPD polyimide after thermal imidization contained approximately half
polyamide. The polyamide depends on the photoalignment characteristics. It is
expected that the photoalignment characteristic of CBDA-TeMPD is different from
those of DSDA-TeMPD and 6FDA-TeMPD.
The UV spectra from 2.5 to 6.5 eV of these LPUV-irradiated TeMPD-based
polyimides for 10 J/cm
2 , unirradiated TeMPD-based polyimides, and TeMPDbased polyamides are shown in Fig. 20. Strong peaks near 6.2 eV were observed
in DSDA-TeMPD and 6FDA-TeMPD. The peak position shifted to 5.5 eV after
thermal imidization, and the energy after imidization was lower than that before
imidization. In addition, the peak intensity decreased after LPUV irradiation. Moreover, weak peaks near 4.4 eV were observed in DSDA-TeMPD and 6FDA-TeMPD
before imidization. The peak position shifted to 4.0 eV after thermal imidization and
LPUV irradiation. In contrast, a strong peak near 6.0 eV was observed in CBDATeMPD before thermal imidization; the peak intensity decreased without a change in
the peak position. A weak peak near 4.5 eV was newly found after thermal
imidization and LPUV irradiation. There was no change in the intensity and position
18 Photoalignment of Liquid Crystal Molecules Using Fluorine-Containing. . .
515