Gas Separation Performance of Polycarbonate Membranes Modified With Multifunctional Low Molecular‐Weight Additives

Abstract

The gas permeation performances and various physical properties of dense polycarbonate (PC) membranes containing low molecular‐weight additives (LMWA) with functional groups were evaluated. The selected LMWAs were p‐nitroaniline, 4‐amino 3‐nitro phenol, catechol and 2‐hydroxy 5‐methyl aniline, and LMWA concentration in the membrane was changed between 1 and 10% (w/w). The PC/LMWA membranes had higher ideal selectivities but lower permeabilities than pure PC membrane. The most effective LMWA which provided the highest selectivity and the lowest permeability in membranes was p‐nitroaniline and the least effective one was catechol. The selected LMWAs antiplasticized the PC matrix and improved the separation performances even at low concentrations. The glass transition temperature (T_g) of PC/LMWA membranes was lower than that of pure PC membrane. Reduction of T_gs as a function of p‐nitroaniline concentration obeyed to Gordon‐Taylor model which indicates antiplasticization type interaction. FTIR spectra of pure and blend membranes also demonstrated the existence of interaction.

Keywords:

• Gas separation
• polycarbonate
• low molecular‐weight additive
• antiplasticization
• glass transition temperature

Acknowledgements

The authors would like to thank the Scientific and Technological Research Council of Turkey (TUBITAK) and METU Research Fund for their financial support with the grant numbers of 104T329 and BAP‐2002‐03‐04‐05.