Synthesis and Characterization of Monodisperse Ferroelectric Side Chain Liquid-Crystalline Siloxane Oligomers
| Autor: | Yoshio Imai, Nawalage F. Cooray, Masa-aki Kakimoto, Yoshiichi Suzuki |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Macromolecules. 28:310-315 |
| ISSN: | 1520-5835 0024-9297 |
| DOI: | 10.1021/ma00105a043 |
| Popis: | The synthesis and characterization of monodisperse ferroelectric side chain liquid-crystalline siloxane oligomers (from monomer to pentamer) having a mesogenic group consisting of (S)-(-)-4-(((2-methylbutyl)oxy)carbonyl)phenyl 4'-(octyloxy)biphenyl-4-carboxylate are described. The controlled hydrolysis of dichloromethylsilane with water resulted in a mixture of α,ω-dichloro-α,ω-dimethylsiloxane oligomers. These were then fractionated by distillation and end-capped with trimethylsilanol sodium salt. The hydrosilylation of the methylsiloxane oligomers with the vinyl mesogen was carried out in the presence of platinum divinyltetramethylsiloxane catalyst. All the oligomers displayed S A and S C * mesophases. A very steep increase of transition temperatures (clearing as well as S A -S C * transition) was observed until the trimer, and then the increase became less steep as the degree of polymeriiation increased. The d-spacing of the oligomers in the S A phase, determined by X-ray diffraction studies, agreed with the length of the repeat unit witch was calculated by molecular simulation. Tits suggested that the S A phase had a monolayer structure. The tilt angle of the S C * phase reached saturation at about 20°C below the S A -S C * transition point (T c -20°C). The fastest response time of 260 μs was observed with the dimer. At T c -10°C, P s values varied in the order monomer< trimer< dimer< pentamer< tetramer, revealing an odd-even effect, wherein the largest P s value of 90 nC/cm 2 was observed for the tetramer |
| Databáze: | OpenAIRE |
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