Influence of crosslinking technique on the physical and transport properties of ethynyl-terminated monomer/polyetherimide asymmetric membranes

Integrally-skinned asymmetric membranes prepared from blends of polyimides and a reactive monomer were prepared and treated with various energy source s to promote crosslinking. The extent of crosslinking was monitored through differential scanning calorimetry measurements. The influence of crosslink ing on the physical and transport properties was measured. Activation proce dures included irradiation (UV, gamma, and electron-beam) and thermal (at t emperatures above and below the glass transition temperature of the polymer ). Surface treatment by irradiation resulted in modest improvements in sepa ration selectivity with little reduction in fast gas flux. Limited conversi on of the ethynyl moieties was achieved (average < 20%). This resulted in n egligible improvements in chemical resistance or thermal stability. Irradia tion using an electron-beam appears to have lead to polymer chain scission resulting in a reduced thermal stability and glass transition temperature. Thermal treatments resulted in high or complete ethynyl conversion. Complet e conversion of the ethynyl units resulted in marked improvements in the re sistance to chemicals, thermal stability, and gas selectivity. Because the reaction temperature was higher than the glass transition temperature of th e fully reacted blend, collapse of the membrane substructure occurred accom panied by a reduction in membrane permeance. Conversely, thermal treatment at 180<degrees>C resulted in a marked increase in the permeance of the memb ranes with a small reduction in selectivity. (C) 2001 Elsevier Science B.V. All rights reserved.