Ultrathin Polyamide Research Articles

Interfacial polymerized thin-film composite membranes for pervaporation separation of aqueous isopropanol solution

High-performance polyamide thin-film composite membranes were successfully prepared using interfacial polymerization of triethylenetetramine (TETA) and trimesoyl chloride (TMC) on the surface of a modified polyacrylonitrile (mPAN) membrane for alcohol dehydration by pervaporation. Attenuated total reflection infrared spectroscopy (FTIR-ATR), scanning electron microscope (SEM), atomic force microscope (AFM) and the contact angle were used to characterize the chemical structures, morphologies and hydrophilicity of the composite membrane active layers. The best pervaporation performance was achieved by using the TETA–TMC/mPAN composite membrane that is prepared by immersing mPAN in 0.1 wt.% aqueous TETA solution for 5 s and then contact with 0.05 wt.% organic TMC solution for 10 s. The pervaporation separation of a 70 wt.% isopropanol–water mixture through the composite membrane with the ultra thin polyamide layer at 70 °C, the permeation rate and water concentration in permeate were 3.4 kg/m 2 h and higher than 99 wt.%, respectively. It was also found that TETA–TMC/mPAN exhibited superior performance to the composite membranes discussed in the literature.

New Experimental Approaches for the Study of Polymer/Metal Interphases

Abstract In this short review we present recent experiments which can be used to infer the structural parameters of ultrathin polyimide and polyamide acid films as a function of distance from the substrate surface. The polyimide films are prepared by the Langmuir-Blodgett technique in a layer-by-layer fashion, and the orientation of the pyromellitic imide unit in the polyimide macromolecules is determined as a function of film thickness by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. Subsequent delamination experiments on these Langmuir-Blodgett (LG) deposited polyimide films reveal that the locus of failure does not occur in a “weak boundary-layer” adjacent to the silicon substrate as expected from delamination experiments with macroscopically thick films. As a non-destructive method to study the orientation of polymer molecules during film growth, second harmonic generation (SHG) experiments on the deposition of polyamide acid (PAA) on gold and silver surfaces will be briefly describ...

Interfacial Synthesis in the Preparation of Reverse Osmosis Membranes

Abstract Reverse osmosis membranes are currently finding increasing use in the production of potable water from salt-laden water sources, and in the purification and recycle of industrial process waters. Most reverse osmosis membranes are comprised either of polyamide hollow fibers or cellulose acetate sheet films. A new type of reverse osmosis membrane, made by the interfacial synthesis of ultrathin membranes directly on microporous support media, is being explored. Two types of interfacially formed membranes are specifically described. One is based on an ultrathin polyamide barrier layer made by interfacial reaction of polyethylenimine with isophthaloyl chloride. The barrier material is supported by a heat-polymerized intermediate zone of polyethylenimine, supported in turn by a microporous polysulfone substrate. The second membrane consists of a polyamide formed from piperazine and a mixed acyl halide reagent. This nonpolymeric amine leads to a different surface texture and the absence of an intermediate zone between the barrier film and the microporous polysulfone substrate. This latter membrane exhibits excellent water fluxes (as high as 4.0 m3/m2 -day at 100 atm) under seawater reverse osmosis test conditions, and shows very high rejection (99+%) of inorganic salts containing polyvalent anions. Differences in the morphology of the salt barrier layers for these two cases are described, and the resulting effects on membrane desalination properties are discussed.