| 초록 |
A novel liquid crystalline polymer composed of oxyethylene backbone and (6-n-heptylsulfonyl)hexylthiomethyl side chains (HSHTP) was synthesized by chemical modification of poly[oxy(chloromethyl)ethylene from the following chemical reactions. (6-n-Heptylsulfonyl)hexanol was obtained in high yield from oxidation of (6-n-heptylthio)hexanol, which was prepared by alkylation of 6-mercapto-1-hexanol. Mesylation of (6-n-heptylsulfonyl)hexanol followed by a substitution reaction using thiolacetic acid yielded (6-n-heptylsulfonyl)hexyl thioacetate. Then, HSHTP was made by a reaction of poly[oxy(chloromethyl)ethylene] and (6-n-heptylsulfonyl)hexyl thioacetate with sodium ethoxide in DMAc. The structure and the effect of the polar sulfone group on the thermotropic mesomorphic behavior was studied using X-ray, differential scanning calorimetry, polarizing optical microscopy, and IR spectroscopy methods. The DSC heating thermogram showed that HSHTP has two transitions at ~57℃ (T1) and ~99℃ (T2). The fiber X-ray pattern at room temperature exhibits a series of ordered reflections (orders of 42.1Å) along the equator and a sharp reflection at d = 4.35 Å intensified on the meridian, characteristics of a smectic B(SB) structure with layer thickness of 42.1 Å. The layer thickness indicates a double layer structure with an all-trans conformation in the alkl side chains. The d-spacing value, 4.35 Å, of the wide angle reflection suggests that the smectic mesophase of HSHTP devleops through dipole-dipole interaction between sulfone groups. Upon heating, this d-spacing increases step-wise to ~ 4.5Å at T1 without losing long-range order in the layers, suggesting that the slightly dilated SB structure remains after T1. Infrared spectroscopy shows that the relative intensities of the sulfone vibration bands at 1325 cm-1 and 1135 cm-1 decrease abruptly at ~ T1 during heating, suggesting that the decrease of sulfone dipole-dipole interactions might be involved in the transition at T1. (Hexadecylsulfonyl)methyl-substituted poly(oxyethylene) (16SP), (Hexadecylthio)methyl-substituted poly(oxyethlene) (16TP), [(6-nonylsulfonyl)hexylthio] methyl-substituted poly(oxyethylene) (9S6TP) and [(6-nonylsulfonl)hexylsulfonyl]methyl-substituted poly(oxyethylene) (9S6SP) were also synthesized to study the effect of the position and the concentration of the sulfone group on the liquid crystalline behavior. 9S6SP, 9S6TP, and 16SP, which contain at least one sulfone group in the side chain, were found to be liquid crystalline, while and 16TP, which does has any sulfone group, showed side chain crystallization behavior. The ordered phase of the polymers was studied using differential scanning calorimetry, cross-polarizing optical microscopy, and X-ray diffraction. |
