Bumsuk Jung

High permeate flux of PVA/PSf thin film composite nanofiltration membrane with aluminosilicate single-walled nanotubes

A new type of thin film nanocomposite (TFN) membranes for nanofiltration was successfully prepared by incorporating aluminosilicate single-walled nanotubes (SWNTs) within the poly(vinyl alcohol) (PVA) matrix. The nanocomposite PVA film was composed of well dispersed synthesized aluminosilicate SWNT with up to 20% volume fraction cast on a polysulfone support. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) revealed that the TFN membranes have characteristic bands at 920-1010 cm(-1) corresponding to Si-OH and Si-O-Al stretching vibration of the aluminosilicate SWNT. This insinuated the successful incorporation of aluminosilicate SWNT into the polymer matrix, which was further confirmed and quantified by X-ray photoelectron spectroscopy (XPS). The PVA layers, in the range of 0.99-1.36 μm, are free from large defects or cracks as observed in the scanning electron microscopy (SEM) images. The membrane surface hydrophilicity increased as the membrane roughness decreased and as the contact angles decreased from 64.2° to 59.4-50.5°. The increase in water flux is due to the presence of hydrophilic nanotubes. With the incorporation of the aluminosilicate single-walled nanotubes, higher permeate water flux was achieved, while sustaining high rejection of divalent ions (97%) and monovalent ions (59%).

Vertically aligned anatase TiO2 nanotubes on transparent conducting substrates using polycarbonate membranes

6 μm-thick, anatase TiO2 nanotubes (NTs) that were vertically aligned to transparent conducting oxide (TCO) substrates were prepared using a sol–gel process and track-etched polycarbonate (PC) membranes.

Controlling gas permeability of a graft copolymer membrane using solvent vapor treatment

AbstractA strategy is reported that combines assembled nanostructures and solvent vapor treatment to manipulate the gas permeability of graft copolymer membranes. The VC-g-POEM graft copolymer consists of poly(vinyl chloride) (PVC) main chains and poly(oxyethylene methacrylate) (POEM) side chains, and was synthesized via atom transfer radical polymerization (ATRP). When the PVC-g-POEM membrane was treated with a good solvent vapor such as acetone, the CO2 permeability increased from 107 to 145 Barrer (1 Barrer=10−10 cm3(STP)·cm·cm−2·s−1·cmHg−1), which is approximately a 36% improvement compared to an untreated sample. However, the permeability was significantly reduced from 107 to 45 and 38 Barrer upon being treated with a selective (methanol) or poor solvent (hexane). The structure-property relation of the solvent-vapor-treated membranes was investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) analysis.

Synthesis and Characterization of Di-hexyl-fluorene and Triphenylamine Based Copolymers Containing 1,3,4-Oxadiazole Pendants

π-Conjugated polymers, poly(N-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)phenyl)-4-(9,9-dihexyl-9H-fluoren-2-yl)-N-phenyl-benzenamine (TPAOXDPF) and poly(N-(4-butylphenyl)-4-(9,9-dihexyl-9H-fluoren-2-yl)-N-phenylbenzenamine) (TPAPF), were synthesized for light emitting diode application. The electron transporting unit, conjugated 1,3,4-oxadiazole, is attached on the main chain as a pendant. The copolymers were thermally stable up to 393°C. The electroluminescent (EL) device based on TPAOXDPF (ITO/TPAOXDPF/Al) has an efficiency of 0.018 cd/A, which is significantly higher than that of the device based on TPAPF (ITO/TPAPF/Al) (0.008 cd/A). This is due to that 1,3,4-oxadiazole pendants improve the electron transporting properties in the emissive layer.