OPTICAL-PROPERTIES OF SIDE-CHAIN LIQUID-CRYSTAL COPOLYMERS OF MONOSUBSTITUTED CHOLESTERYL ITACONATE AND A NONCHIRAL MESOGEN

Citation
Jmg. Cowie et Hw. Hunter, OPTICAL-PROPERTIES OF SIDE-CHAIN LIQUID-CRYSTAL COPOLYMERS OF MONOSUBSTITUTED CHOLESTERYL ITACONATE AND A NONCHIRAL MESOGEN, Canadian journal of chemistry, 73(11), 1995, pp. 1811-1817
Citations number
16
Categorie Soggetti
Chemistry
ISSN journal
00084042
Volume
73
Issue
11
Year of publication
1995
Pages
1811 - 1817
Database
ISI
SICI code
0008-4042(1995)73:11<1811:OOSLCO>2.0.ZU;2-H
Abstract
New mono- and disubstituted cholesteryl derivatives of itaconic acid h ave been prepared and their thermotropic liquid crystalline behaviour examined. The monosubstituted derivative has been homopolymerized, and also copolymerized with a non-chiral mesogen 4-cyanophenyl-4'-(6-acry loyl oxyhexyloxy) benzoate. Examination of the series of copolymers pr epared, using differential scanning calorimetry and hot-stage polarizi ng microscopy, showed that when the content of the cholesteryl itacona te was high, both a smectic-A phase (S-A) and a cholesteric phase (N) were present. It was found that the S-A phase could be eliminated by lowering the content of the cholesteryl itaconate in the copolymers, g iving samples that displayed only the N phase over a much wider tempe rature range. The samples in the N phase also exhibited selective ref lection of visible light that changed from short to long wavelengths a s the samples were cooled from the isotropic melt. These colours can b e locked into the glassy state of the polymer by quenching below the g lass transition temperature, but only if the S-A phase is absent. It w as also noted that at high contents of the cholesteryl itaconate the s elective reflection appears to occur in the ultraviolet region.