• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.6
• /
• pp.481-485
• /
• 1998

We investigated the generation of high pretilt angle for nematic liquid crystal (NLC) in a cell with obilique non-polarized ultraviolet (UV) light irradiation on mixtured polyimide surface. It was found that the monodomain alignment of NLC is obtained with an angle of incidence of 75∼85 degrees on PI surface. We consider that the monodomain alignment of NLC is attributed to anisotropic dispersion force effect to photo-depolymerization of polymer. We successfully observed that the pretilt angle of NLC is generated above 5 degree with an angle of incidence of 75∼85 degrees. It is considered that the pretilt angle generation NLC is attributed to interaction between the LC molecules and the polymer surfaces.

• Applied Chemistry for Engineering
• /
• v.8 no.5
• /
• pp.853-859
• /
• 1997

For asymmetric polyetherimide membranes having a dense layer gradient structure on the skin layer, the morphology change and pervaporation behaviors of water/isopropanol mixture through chemical modification of dense skin layer were investigated. The extent of the density was controlled by the evaporation, time, and when the evaporation time was increased from 0 min to 4 min, the permeation flux was decreased, the separation factor was increased. Also, the pervaporation behaviors of the polyetherimide membranes modified with sodium hydroxide solution, as the modification time of dense skin layer increased, the selectivity increased, and the permeation flux decreased. The morphology change identified by SEM shows that the density of dense skin layer tends to increase with increasing modification time, this result is consistent with above observations.

• Applied Chemistry for Engineering
• /
• v.8 no.6
• /
• pp.945-953
• /
• 1997

Aromatic polyetherimide membranes were prepared by dry/wet phase inversion method and investigated regarding the pervaporation characteristic of water-alcohol mixtures by using the permselective property of imide group and the structure modification of skin layer of the membrane. The membrane selectivity increased with the reaction time of surface-modification, to some extent, and the density of top layer tends to increases with increasing the reaction time. In the case of dense membrane, the separation factor was 160 and 2000 for 90wt% ethanol mixture and 90wt% isopropanol solution, respectively, which implies that aromatic polyetherimide has a high permselectivity. The temperature dependence of permeation flux seems to follow an Arrhenius type at the temperature range of ($40^{\circ}C-70^{\circ}C$).

• Membrane Journal
• /
• v.23 no.6
• /
• pp.432-438
• /
• 2013

Mixed-matrix membranes (MMMs) containing MIL-100(Fe), a MOF type, were fabricated in this study. MMMs up to 30 wt% MOF loading were prepared, and their gas permeabilities were tested. $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ gas permeabilities increased with the MOF loading, while $SF_6$, the largest kinetic diameter in this study, exhibited reduction of gas permeability with the loading. Ideal gas selectivity of $N_2/SF_6$ improved by 40% as compared with pure polyimide membrane, suggesting the proposed MMMs were suitable for $N_2/SF_6$ separation.