研究目的
Investigating the photo-switching orientation behavior of nematic liquid crystals on a high-density brush of an azobenzene-containing side chain liquid crystalline polymer, focusing on azimuthal and zenithal control.
研究成果
The high-density azobenzene side chain polymer brush enables reversed photoalignment modes compared to traditional systems, with stable azimuthal control via linearly polarized visible light and reversible zenithal switching with UV light, offering new possibilities for liquid crystal alignment technologies.
研究不足
The instability of the homeotropic state after UV irradiation is not fully understood, and the study is limited to specific polymer and NLC systems; broader applicability and long-term stability may require further investigation.
1：Experimental Design and Method Selection:
The study uses surface-initiated atom transfer radical polymerization (SI-ATRP) to synthesize high-density polymer brushes of poly[4’-10-(methacryloyloxy)decyloxy-4-(heptylpheynylazo)phenyl] (PAz) on quartz substrates. Polarized optical microscopy (POM) and polarized UV/vis absorption spectroscopy are employed to analyze nematic liquid crystal (NLC) orientation.
2：Sample Selection and Data Sources:
Quartz substrates are modified with PAz brushes or spincast films. NLC 4’-pentyl-4-cyanobiphenyl (5CB) is used, with dichroic dye LCD118 doped for absorption measurements.
3：List of Experimental Equipment and Materials:
Equipment includes a fluorescence microscope (BX-51-FL, Olympus), CCD camera (DP70, Olympus), multi-channel photo detector (MCPD-2000, Otsuka), Hg-Xe lamp (Supercure-203S, San-ei electronics), and NMR spectrometer (JNM-GSX270, JEOL). Materials include silica particle spacers (
4：0 μm, Tokuyama Corp.), lecithin, 5CB (Merck), and LCD118 (Nippon Kayaku Co.). Experimental Procedures and Operational Workflow:
PAz brushes are synthesized via SI-ATRP. LC cells are fabricated by sandwiching NLC between substrates, with one side modified. Irradiation with UV (365 nm) and visible (436 nm) light is performed at specified doses. POM and absorption measurements are conducted before and after irradiation.
5：Data Analysis Methods:
Orientation order parameters are calculated from dichroic ratios in absorption spectra. POM images are analyzed for texture changes.
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fluorescence microscope
BX-51-FL
Olympus
Used for polarized optical microscopy observations of liquid crystal cells.
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CCD camera
DP70
Olympus
Used for capturing images during microscopy observations.
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NMR spectrometer
JNM-GSX270
JEOL
Used for 1H-NMR measurements to characterize polymer brushes.
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multi-channel photo detector
MCPD-2000
Otsuka
Used for measuring polarized UV/vis absorption spectra.
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Hg-Xe lamp
Supercure-203S
San-ei electronics
Used as a light source for UV and visible light irradiation.
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silica particle spacer
6.0 μm
Tokuyama Corp.
Used as spacers in liquid crystal cell fabrication to control cell gap.
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liquid crystal
5CB
Merck
Used as the nematic liquid crystal in the experiments.
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dichroic dye
LCD118
Nippon Kayaku Co.
Doped in the liquid crystal for polarized absorption measurements.
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