Orientational behavior of side-chain liquid-crystalline polysiloxanes deduced from measurements of second harmonic generation
✍ Scribed by Nobukatsu Nemoto; Yu Nagase; Jiro Abe; Hiroshi Matsushima; Yasuo Shirai; Nobuo Takamiya
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 600 KB
- Volume
- 196
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Side‐chain functionalized polysiloxanes were prepared via polymer‐analogous esterification of poly[(3‐chloroformylpropyl)methylsiloxane] with 4‐(4‐hydroxyphenylazo)nitrobenzene (P1), 4‐[4‐(ω‐hydroxyalkyloxy)phenylazo]nitrobenzene (P2–P4), 4‐{4‐[N‐(2‐hydroxyethyl)‐N‐methyl]anilinoazo}nitrobenzene (P5), 4‐(4‐hydroxypiperidino)nitrobenzene (P6), or 4‐[4‐(2‐hydroxyethyl)piperidino]nitrobenzene (P7)., P1, P3, P4 and P5 exhibit liquid crystallinity, as deduced from differential scanning calorimetry, polarized microscopic observations and X‐ray diffraction measurements. The liquid‐crystalline phase of P1 and P5 is a nematic phase, and that of P3 and P4 is a smectic one. The second harmonic generation (SHG) measurement of a spin‐coated film of P1 was carried out by the Maker fringe method using a Q‐switched Nd:YAG laser (1064 nm). The SHG profile after the heat treatment of a spin‐coated film suggests a perpendicular orientation of the mesogenic molecules to the glass substrate. The SH light intensity of a corona‐poled film was 20‐fold higher than that of a film which was only heated, though no differences were observed in their UV‐vis absorption spectra. These findings suggest that the mesogenic‐molecular dipole moments are aligned to the same direction in the crystalline or liquid‐crystalline phase by a poling treatment.