Preparation and characterization of thin parlodion membranes

Abstract

synopsisParlodion membranes 95 to 500 A. thick have been prepared on a glass surface by dipping a clean glass plate into the Parlodion solution and subsequently evaporating the solvent under controlled conditions by keeping the glass plate vertical in a metallic frame and covered with an inverted beaker. The membrane may be floated off on to an aqueous surface. Capacitance measurement established the thicknew of the membrane. Electrical resistance and isothermal diffusion potentials arising across them when they separate different salt solutions have also been measured at room temperature.In a previous study,' it was found that the electrical resistance of Parlodion membranes and isothermal diffusion potentials arising across them when they separated different salt solutions, decreased with increase in membrane thickness which was built by transferring more of the Parlodion solution to cover a fixed area of the aqueous surface. It was suggested that the increase in porosity of the membrane and masking of the effect of some of the ionogenic carboxyl groups present as the thicker membranes were formed, were probably responsible for the observed decrease in the membrane resistance and the emf.In order to confirm these suggestions, thin membranes (95-500 A. thick) were prepared by a different technique. The thickness of the membrane was developed not by using larger volumes of the standard Parlodion solution but by increasing the concentration of the membrane-forming solution. This principle is inherent in the method of membrane formation developed by Carnell and Cassidy.2 In our previous attempt^,^ difliculty was experienced in floating the membrane off the glass plate on to an aqueous surface. Further, there was the uncertainty about membrane thickness and hence required another independent method to infer the thickness. But recent work' has shown that this uncertainty can be eliminated by measuring the membrane capacitance. Use of the General Radio impedance-admittance (2-Y) bridge to measure the resistance of the membrane gave also the required capacitance value from which the thickness of the membrane could be deduced. 1285

Review of laboratory methods for the preparation of polymer films

“…Dipping a glass plate into polymer solutions and removing it vertically is another laboratory technique for film preparation (1, 9, 13, 79, 80, 85). The rate of withdrawal of the plate influences the thickness of the resulting film.…”