1. Synthesis of photo-sensitive polymers containing carbon-carbon double bond side groups for application on photo-alignment of liquid crystals 1 Reporter : Chih-Hao Li Advisor : Ching-Dong Hsieh Date: 100.09.28

2. 2 Report of last semester

3. 3 Introduction Introduction Paper review Paper review Motivation Motivation Experimental Experimental Results and discussion Results and discussion Conclusions Conclusions Future work Future work Outline

4. 4 IntroductionIntroduction Nowadays, the mechanical rubbing of polyimide (PI) and polystyrene (PS) substrates has been widely studied as a method of fabricating LC alignment layers. However, the rubbing process has disadvantages such as electrostatic charge, dust generation, and physical damage to the alignment layer surfaces. Alignment layer Glass plate Rubbing roll Move direction Rubbing alignment

5. 5 Photoalignment has been taken a notice of promising noncontact alignment techniques to be used for the next generation LC display applications, due to its various advantages such as its cleaness, suitability for large glass substrates, and unrestrictedness to surface morphology. Photo-alignment Polarizer θ Alignment layer Glass plate UV Source

6. 6 Photo-reaction hυhυ Fig. 1. Photochemical reaction mechanisms of PCEMA, (a)E–Z isomerization reaction,(b) [2+2] photoaddition reaction. or (a) (b)

7. 7 Paper review

8. 8

9. 9 MotivationMotivation In order to utilize the anisotropic distribution of photodimers of photocrosslinkable polymers for the molecular orientation film, the stable orientation of photodimers is required. However, the practical applications of photocrosslinkable polymers are quite restricted due to significant thermal relaxation of the photocrosslinkable polymers at high temperature, which causes the randomization of photodimers. The synthesis, photo-reaction and photo-induced liquid crystals(LC) alignment of methacrylate homopolymer(PCEMA) containing cinnamate side group are reported in this work. The polymers were blended with crosslinking agent (DOD-Ci) to enhance thermo-stability. In this research, we use the photo-alignment method to improve the disadvantages of the rubbing method, and investigated the photo-reaction and alignment Properties of alignment films.

10. 10ExperimentalMaterials Cinnamoyl chloride 4,4’-Biphenol DOD 2-Hydroxyethyl methacrylate HEMA 2,2'-Azobis(2-methylpropionitrile) AIBN Triethylamine TEA Ethyl acetate EAc Hexane Propan-2-ol IPA Tetrahydrofuran THF Cinnamoyl chloride DOD HEMA

11. HEMA(10g, 77mmol) and AIBN(0.38g, 2.3mmol) were dissolved in IPA(80mL). 11 Water bath (60 ℃ ) Stirring was maintained for 24 h. Stirring was maintained for 24 h. The cooled reaction solution and added dropwise with vigorous stirring to mixed solution of Hexane and EAc. Dissolved again in IPA and reprecipitated from mixed solution. This procedure was repeated until no more monomer was present by PHEMA and a white solid was obtained(7.25 g, yield 72.5%). Synthesis of PHEMA

12. 12 Synthesis of photosensitive polymer PCEMA PHEMA(0.5g, 3.8mmol) and TEA(0.77g, 7.6mmol) were dissolved in THF(15mL). Cinnamoyl chloride(1.27g, 7.6mmol) was dissolved in THF(10mL). Stirring was maintained for 24 h. Stirring was maintained for 24 h. Ice bath(0 ℃ ) The precipitate was filtered, washed with Na 2 CO 3 solution, and water. The precipitate was filtered and dried under vacuum to give 71% of PCEMA.

13. DOD(1.12g, 6mmol) and TEA(1.82g, 18mmol) were dissolved in EAc(20mL). Ice bath(0 ℃ ) Cinnamoyl chloride(3g, 18mmol) was dissolved in EAc(15mL). 13 Stirring was maintained for 24 h. Stirring was maintained for 24 h. Synthesis of cross-linking agent DOD-Ci The precipitate was filtered, washed with Na 2 CO 3 solution, and water. Finally, the solvent of the dried filtrate was evaporated under reduce pressure and dried under vacuum to give 82% of DOD-Ci.

14. 14 LC cell assembly 45° Glass substrate PCEMA+ Chloroform spin coating UV light: 7.94J/cm 2 13cm Spacer(30μm) Liquid crystal LC cell

15. 15 Results and discussion Fig. 2. FT-IR spectrum of (a) HEMA, (b) PHEMA. (a) (b) C=C(1625 cm -1 ) Structure identification of polymer and compound

16. 16 Fig. 3. FT-IR spectrum of (a) PCEMA, (b) DOD-Ci. (b) (a) PCEMA DOD-Ci -OH(3200-3600 cm -1 )C=C (1650 cm -1 ) O-C=O(1765 cm -1 、 1705cm -1 ) C-O-C(1040 cm -1 )

17. 17 Fig. 4. 1 H NMR spectra of the DOD-Ci. Theoretical values =1:1:9 Actual values =0.99:1:9.01 a b c a b c c c a a b b c cc c

18. 18 Fig. 5. 1 H NMR spectra of the PCEMA. Theoretical values =1:1:5:4 Actual values =0.99:1:5.16:3.71 a b c d c c c a a b b d d

19. 19 Photochemical reaction Fig. 6. The change of UV absorbance of polymer and compound solution with UV irradiation, (a)PCEMA, (b) DOD-Ci. (a)(b) 290nm The UV-Vis spectra of cinnamate-containing monomer (DOD-Ci) and polymer PCEMA shows that C=C double bond disappears after UV irradiation for 30 min.

20. Before irradiation After irradiation Fig. 7. 1 H NMR spectra of DOD-Ci before and after UV irradiation for 30min. a a b b c cc c ab c c c a’ b’ a’ b’ d d d

21. 21 Fig. 8. The change of UV absorbance of polymer solution with UV irradiation, (a)PCEMA, (b)PCEMA/DOD-Ci = 9/1, (b)PCEMA/DOD-Ci = 8/2, (b)PCEMA/DOD-Ci = 7/3. (a) (b) (c) (d) 290nm

22. 22 Alignment Property a a b b a a b b Fig. 9. Photographs of (a) 0° dark and (b) 45° bright states of LC cells under polarised microscopy. Cells were prepared using PCEMA as Rubbing alignment and Photo-alignment coating. Rubbing alignment photo-alignment Polarizer Direction: Groove

23. 23 Fig. 10. Photographs of 0° dark and 45° bright states of LC cells under polarised microscopy. Cells were prepared using (a)PCEMA/DOD-Ci = 9/1, (b)PCEMA/DOD-Ci = 8/2, and (c)PCEMA/DOD-Ci = 7/3 as photo-alignment coating. a a b b c c Polarizer Direction: Dark state Bright state

24. 24 Thermal stability Fig. 11. Photographs of 0° dark and 45° bright states of LC cells under polarised microscopy. Cells were prepared using (a)PCEMA, (b)PCEMA/DOD-Ci = 9/1, (c)PCEMA/DOD-Ci = 8/2, and (d)PCEMA/DOD-Ci = 7/3 as photo-alignment coating and then annealed at 100 ℃ for 1h. a a b b c c d d Polarizer Direction:

25. 25Conclusions 1 H NMR showed that DOD-Ci and PCEMA was synthesized sucessfully and actual values of peak area was consistent of theoretical values. The UV-vis spectra of cinnamate-containing DOD-Ci and polymer PCEMA shows that C=C double bond disappears after UV irradiation for 30min, and as the weight percent of the DOD-Ci increased from 0 to 30%, the photostability times of the polymer decreased from 30min to 4min. DOD-Ci containing cinnamate groups can produce E–Z isomerization and [2+2] photoaddition reaction upon their exposure to nonlinearly polarized ultraviolet (NP-UV) light. The POM images of the LC cell placed between two crossed polarizers show dark and bright states when the cell was rotated from 0 to 45° with respect to the polarization direction. 1 H NMR showed that DOD-Ci and PCEMA was synthesized sucessfully and actual values of peak area was consistent of theoretical values. The UV-vis spectra of cinnamate-containing DOD-Ci and polymer PCEMA shows that C=C double bond disappears after UV irradiation for 30min, and as the weight percent of the DOD-Ci increased from 0 to 30%, the photostability times of the polymer decreased from 30min to 4min. DOD-Ci containing cinnamate groups can produce E–Z isomerization and [2+2] photoaddition reaction upon their exposure to nonlinearly polarized ultraviolet (NP-UV) light. The POM images of the LC cell placed between two crossed polarizers show dark and bright states when the cell was rotated from 0 to 45° with respect to the polarization direction.

26. 26 Future work + + DCC K 2 CO 3 Synthesis of PHEMA derivatives containing photo-reactive side groups.

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28. 28 Thanks for your listening!