DEVELOPMENT AND CHARACTERIZATION OF HOMOGENEOUS MEMBRANES DE FROM HIGH-MOLECULAR-WEIGHT SULFONATED POLYPHENYLENE OXIDE

The high molecular weight polyphenylene oxide (PPO) was sulfonated to different ion exchange capacity (IEC) values using chlorosulfonic acid . The physico-chemical properties along with the gas transport propert ies of the membranes prepared from sulfonated PPO (SPPO) were evaluate d. Sulfonation of PPO results in a linear increase of density with the IEC value while the average d-spacing in polymer remains constant. Su lfonic groups attached to the aromatic ring in the PPO backbone are no t thermally stable. On the other hand, when tested with CO2 at room te mperature, the SPPO membranes maintained a constant permeability over the period of 60 days. An increase in IEC value of SPPO results in an increase in O-2/N-2 and CO2/CH4 ideal selectivities and a decrease in O-2 and CO2 permeabilities. The combination of permeability and ideal selectivity for both gas pairs places the SPPO membranes below the res pective upper-bound lines for polymeric membranes. However, an increas e in the IEC value brings the permeability versus ideal selectivity re lationship closer to the upper-bound Line, especially for the O-2/N-2 gas pair. (C) 1998 Elsevier Science B.V. All rights reserved.