Boltorn-modified polyimide gas separation membranes

This paper describes the preparation, characterization and permeation properties of polyimide BTDA-AAPTMI (Matrimid 5218) and co-polyimide BTDA-TDI/MDI (P84) dense polymer films containing aliphatic hyperbranched polyesters, Boltorn (H40). The H40 are dispersed in the polymers at various concentrations.\ud \ud For Matrimid–H40 1.0 wt% membrane the nitrogen permeability increases but with significant loss in selectivity, while at higher H40 concentrations (5.0 and 10.0 wt%) the permeability becomes lower than of the pure polymer and the selectivity generally stays constant. The dispersion of various concentrations of H40 (1.0, 5.0 and 10.0 wt%) in P84 membranes decreases gas permeability in comparison to pure P84, while the selectivity generally stays constant

Fullerene-Modified Poly(2,6-dimethyl-1,4-phenylene oxide) Gas Separation Membranes: Why Binding Is Better than Dispersing

This paper describes the preparation, characterization, and the permeation properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) dense polymer films containing fullerenes (C60). The C60 are either dispersed or covalently bonded to PPO at various concentrations. The gas permeability results are very different between covalently bonded and dispersed PPO−C60. The gas permeability of PPO−C60 bonded increases up to 80% with increasing fullerene concentration. The gas pair selectivity, however, stays constant. This behavior is probably due to stiffening of the polymer structure and increase of free volume. The gas permeability through the PPO−C60 dispersed decreases in comparison to pure PPO. This reduction is due to C60 clustering in the polymer. The clusters seem to induce polymer crystallinity, and they are probably aligned along the film plane, creating an extra barrier for gas permeation

Free Volume in C60 Modified PPO Polymer Membranes by Positron Annihilation Lifetime Spectroscopy

PPO (poly(2,6-dimethyl-1,4-phenylene oxide)) is a well-known membrane material showing good gas separation properties. The incorporation of nanoparticles can enhance or deteriorate the performance of composite membranes, sometimes depending only on the way of the composite preparation. We have modified the PPO polymer with C60 fullerenes up to a content of 2 wt %. Previous investigations showed a strong dependence of permeability on whether the C60 is simply dispersed in the polymer or chemically bonded to the polymer chains. Free volume effects were suggested as an explanation but not experimentally confirmed. Here, we present free volume studies by positron annihilation lifetime spectroscopy. An additional long positron lifetime shows the increased free volume of composite samples, while the high electron affinity of C60 helps to indicate the homogeneity of the samples. Combining the presented results with permeability measurements refines the understanding of this promising membrane material

Boltorn-Modified Poly(2,6-dimethyl-1,4-phenylene oxide) Gas Separation Membranes

This paper describes the preparation, characterization and the permeation properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) dense polymer films containing aliphatic hyperbranched polyesters, Boltorn (H20, H30, and H40). The Boltorn are dispersed in PPO at various concentrations. The gas permeability results were very different between low and high concentration of Boltorn. The gas permeability of PPO with 1.0 wt % of Boltorn is 2−3 times higher than the pure polymer, while at higher concentration (9.1 wt %) of Boltorn the permeability becomes almost 50% of the pure polymer. The gas pair selectivity, however, stays constant. The increase in permeability at low concentration of Boltorn is due to the increase of the free volume, probably due to hydrogen bonds between Boltorn and the oxygen of PPO backbone. The decreased permeability of PPO containing higher concentration of Boltorn (9.1 wt %) is due to two reasons: decrease in free volume as determined by PALS as well as phase separation. The hyperbranced polyesters form aggregates that migrate to the top surface of the membrane

Novel gas separation membranes containing covalently bonded fullerenes

In this work, we report superior mass transport properties of polymers prepared by the covalent coupling of supermolecular carbon cages (e.g., fullerenes, bucky balls) to a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymer. Dispersing the bucky balls into the polymer reduces gas permeability, whereas covalent bonding enhances permeability up to 80% in comparison to the pure PPO. Gas pair selectivity, however, is not compromised and stays constant