of the weak peak. The peaks changed by thermal imidization and LPUV irradiation
were assigned based on the results of the MO calculation.
For the TeMPD-based polyamides and polyimides, orbital compositions of the
frontier MOs are shown in Fig. 21. They are mainly described by one electron
excitation from the HOMO to the LUMO. Consequently, the HOMO!LUMO
transition implies electron density transfer. Note that the charge at HOMO and
LUMO is located on the TeMPD and acid component sites, respectively. That is,
photoabsorption of polyamides and polyimides in the current study depends on the
CT transition from the TeMPD site to the acid component site because of the phenyl
group π–π
à transitions. Calculated UV absorptions of these TeMPD-based polyamides and polyimides are shown in Fig. 22. The peak position slightly shifted
toward 5.3 eV for polyamides and 5.0 eV for polyimides in the case of DSDATeMPD and 6FDA-TeMPD. The peak shifts depend on the imidization reaction, as
shown in Fig. 20. On the other hand, there was no change in the peak position
between polyamide and polyimide in CBDA-TeMPD. This result is in good agreement with the observed UV spectra in Fig. 20.
This behavior is well-known with regard to the formation of CTCs or CT
interactions in polyimides (Kanehashi et al. 2011). This interaction is attributed to
the presence of π electrons between the ring structures in polyimides. The CTC
structure is similar to a sandwich structure between imides and the neighboring
benzene ring. The CT interaction observed during CTC production strongly depends
on the fluorescence spectrum. Figure 23 shows the fluorescence spectra of TeMPDbased polyamides and polyimides before and after thermal imidization and after
LPUV irradiation. These polymers exhibited an emission spectrum band at 470 nm
after excitation at 325 nm. This band is attributed to the intramolecular interactions
Fig. 20 Absorption spectra
of LPUV-irradiated and
unirradiated TeMPD-based
polyimides and polyamides.
(Reprinted with permission
from J. Photopolym. Sci.
Technol. 26, 769. (Copyright
(2013) The Society of
Photopolymer Science and
Technology))
18 Photoalignment of Liquid Crystal Molecules Using Fluorine-Containing. . .
517
were assigned based on the results of the MO calculation.
For the TeMPD-based polyamides and polyimides, orbital compositions of the
frontier MOs are shown in Fig. 21. They are mainly described by one electron
excitation from the HOMO to the LUMO. Consequently, the HOMO!LUMO
transition implies electron density transfer. Note that the charge at HOMO and
LUMO is located on the TeMPD and acid component sites, respectively. That is,
photoabsorption of polyamides and polyimides in the current study depends on the
CT transition from the TeMPD site to the acid component site because of the phenyl
group π–π
à transitions. Calculated UV absorptions of these TeMPD-based polyamides and polyimides are shown in Fig. 22. The peak position slightly shifted
toward 5.3 eV for polyamides and 5.0 eV for polyimides in the case of DSDATeMPD and 6FDA-TeMPD. The peak shifts depend on the imidization reaction, as
shown in Fig. 20. On the other hand, there was no change in the peak position
between polyamide and polyimide in CBDA-TeMPD. This result is in good agreement with the observed UV spectra in Fig. 20.
This behavior is well-known with regard to the formation of CTCs or CT
interactions in polyimides (Kanehashi et al. 2011). This interaction is attributed to
the presence of π electrons between the ring structures in polyimides. The CTC
structure is similar to a sandwich structure between imides and the neighboring
benzene ring. The CT interaction observed during CTC production strongly depends
on the fluorescence spectrum. Figure 23 shows the fluorescence spectra of TeMPDbased polyamides and polyimides before and after thermal imidization and after
LPUV irradiation. These polymers exhibited an emission spectrum band at 470 nm
after excitation at 325 nm. This band is attributed to the intramolecular interactions
Fig. 20 Absorption spectra
of LPUV-irradiated and
unirradiated TeMPD-based
polyimides and polyamides.
(Reprinted with permission
from J. Photopolym. Sci.
Technol. 26, 769. (Copyright
(2013) The Society of
Photopolymer Science and
Technology))
18 Photoalignment of Liquid Crystal Molecules Using Fluorine-Containing. . .
517