Positron Annihilation Study Of Free Volume Holes In Polymeric Membranes And Confirmation By Atomic Force Microscopy

Positron annihilation lifetime spectroscopy (PALS) is a powerful technique for the study of free volume in polymers. The lifetime of ortho-Positronium (o-Ps), a bound state of an electron and a positron, can be used to assess the pore size, while the intensity can be used to characterize the number of pores. PALS is still now an effective physical method on the examination of polymeric membranes. The main goal of this research is to evaluate the free volume of the different membranes.On the basis of the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes in the sulfonated poly(phenylene oxide) (SPPO) membranes with different amount of LiCl and SPPO-PES (Polyethersulfone) blends varying contents ratio, were calculated and compared each other. Free volume can increase from SPPO membrane by doping LiCl, and can decrease by blending with less free volume polymer, PES. And the characterization of sulfonated polyetherketone (SPEK-C) films was investigated on the variation of sulfonation degree and solvent evaporation time of the films. Pore size and distribution were determined from PALS and their results were confirmed by AFM.Positively charged asymmetry membranes from poly(phenylene oxide) by benzyl bromination (BPPO) were also investigated on the different amounts of TMA-DMF solution and effect of different amine solutions. Free volumes of membranes consisted of different amine solution, became significantly decrease. It is due to the less hydrophilic effect of charged groups on the membrane performance. Therefore, free volume can be controlled by changing the hydrophilicity of the charged groups of the membranes.