Photoinduced Reorientation and Polarized Fluorescence of a Photoalignable Liquid Crystalline Polymer
, Moritsugu Sakamoto 2,3, Tomoyuki Sasaki 2,3, Hiroshi Ono 2,3 and Nobuhiro Kawatsuki 1,2,*
Round 1
Reviewer 1 Report
Comments for author File: 
Comments.pdf
Author Response
We have added two references and following sentence in to the text.
“Several studies have studied on the polarized fluorescence of LC materials based on the photoalignment technique [34–37].”
[36] Nasrollahi, A.; Kumar, V.; Lee, M.-H.; Kang, S.-W. In situ planar photoalignment of liquid crystals: two-step interfacial modifications through light–matter interactions actuated by linearly polarized UV-light. J. Mater. Chem. C, 2020, 8, 1722–1735.
[37] Shibata, Y.; Tsunaki, R.; Ishinabe, T.; Fujikake, H. Polarized Photoluminescence Characteristics of Uniaxially-Aligned Fluorescent Dye with Liquid Crystalline Polymer for Agricultural Applications. ITE Trans. on MTA 2021, 9, 203–209.
Reviewer 2 Report
The authors show thermally stimulated photoinduced reorientation of liquid crystalline (LC) which exhibits a significant molecular reorientation (D > 0.7) when the film is exposed to linearly polarized 313nm light and subsequently annealed in the LC temperature range of the material. The paper is well written and for me it can be accepted after the authors answer these comments.
1) why increasing the energy of the laser exposure and the annealing temperature the dicroism vanishes ? The authors should explain better what happens.
2) the authors should decrease the number of abbreviations in the text. Sometimes it can be useful repeat the entire name instead of the abbreviation.
Author Response
Answer to Point 1:
When the exposure dose increases, out-of-plane reorientation of NBA will occur, which reduces the thermal stimulation of the in-plane orientation. Thermal stimulation cannot be generated at the isotropic temperature of the material due to its random motion. We have added a following sentence in the text.
“This is due to out-of-plane motion and side photoreaction of the mesogenic side groups.”
“Random motion above the LC temperature of the film vanishes the photoinduced dichroism.”
Answer to point 2:
According to reviewer’ suggestion, we eliminated several abbreviations.
N-salicylideneaniline (SA) → N-salicylideneaniline
linearly polarized (LP) 313-nm light → linearly polarized 313-nm light
benzoic acid (BA) side groups → benzoic acid side groups
Reviewer 3 Report
This is a great manuscript discussing the development of the new photoalignable liquid crystal polymer comprised of phenyl benzoate mesogenic group connected with an NBA2 end moiety. The polymer could show the large anisotropy and polarized fluorescence which is possible to be used in display and diffraction elements. The manuscript is well organized with clear description and details. And the manuscript references plenty of the high-quality pervious works. As all reasons listed above, I suggest publishing this manuscript if the author could answer these questions:
1. The author have done some study of the UV light exposure and absorption study, however, there is a possible issue. Since the film is highly absorbed with these wavelengths, the exposure dose in the front side and in the back side of the film could be significantly different. Then the film performance might have thickness dependence. The author might give the clarification of this issue.
2. The paper shows the dose dependent anisotropy, it would be great if the author could give more explanation and explore the possible ways to control this dose dependence.
3. In the paper there is lack of the film surface characterization. Especially there is a hydrolysis step which is highly possible changing the surface properties and flatness. It would be great if the author could give more explanation here.
Author Response
Answer to comment 1:
Reviewer’s comment is important for the photoreaction of a photosensitive film. A required exposure energy depends on the film thickness. At present, we have used ~200 nm-thick film for the photoreaction. The further experimental of the effect of the film thickness for the reorientation performance should be carried out. We have tested up to 1000 nm thick film and obtained similar results, but detailed investigation is underway.
Answer to comment 2:
Photoreaction of the film state, such as photocuring, depends on both power of the light source and total exposure energy. Reviewer will require this information. We have only used UV light with bandpass filter, yielding 13 mW. As reviewer suggested, we would like to explore the dependence of the light source power and film thickness.
Answer to comment 3:
Change in the film thickness after the hydrolysis is negligible because the loss of the volume of the monomer (benzaldehyde) is much smaller than the volume of the polymer. As far as the absorption measurements, film’ surface did not obviously change after the hydrolysis. Detailed surface profile will be investigated in the next paper.
