Design of gas separation membranes derived of rigid aromatic polyimides. 1. Polymers from diamines containing di-tert-butyl side groups

Molecular modeling investigation of the fundamental structural parameters of polymers of intrinsic microporosity for the design of tailor-made ultra-permeable and highly selective gas separation membranes

“…It is obvious from the figure that the presence of these fluorine atoms has caused PIM-4 to exhibit higher values for the diffusion coefficients of the various gases than those of PIM-10, which is also correlated with the decrease in the fractional free volume of PIM-10 as illustrated in Table 4. This is very interesting since Alvarez et al, [27] reported that synthesized di-tert-butyl diamine-based PIMs showed exact similar trend experimentally. As the fluorine-rich 4,4 0 -hexafluoroisopropyliden diphthalic anhydride (6FDA) moiety of the PIM is replaced with the 3,3 0 ,4,4 0 -biphenyltetracarboxylic dyanhidride (BPDA) moiety, which had no fluorine atoms, the PIMs showed similar behavior to that predicted theoretically.…”

“…The fractional free volume (FFV) of the 6FDA-PIM has decreased by 20% when converted to BPDA-PIM comparable to the 25% decline in the FFV when PIM-4 was converted to PIM-10 (Tables 2 and 4). Furthermore, the experimentally determined [27] diffusion coefficients of CH 4 , CO 2 and N 2 through 6FDA-PIM have declined to a fourth of their values when the PIM was converted to BPDA-PIM. Quite interestingly, this decline is similar to that predicted for PIM-4 and PIM-10 as shown in Fig.…”

Aromatic poly(ether ether ketone)s capable of crosslinking via UV irradiation to improve gas separation performance

“…In contrast, P(CO 2 ) is close to P(He) and P(CH 4 ) is somewhat higher than P(N 2 ) in the case of TMBP-DFB membrane, which is a typical behavior of polymers having high FFV. [38][39][40] These results suggest that the methyl groups could be partially occupying the void space (internal free volume), which would cause a decrease in both the overall FFV and the size of accessible holes.…”

Synthesis, characterization and gas separation properties of novel polyimides containing cardo and tert-butyl-m-terphenyl moieties

“…A good membrane has to show high permeability, and this is usually attained, in glassy polymers, by means of structural changes that make difficult the molecular packing and increase the free volume [11,12]. The introduction of bulky pendent groups [13][14][15][16], which prevent the close packing of the chains, has been shown as a very efficient method to increase the fractional free volume (FFV) and consequently to enhance the gas permeability. Among the bulky pendent groups introduced into polyimides, tert-butyl groups have shown to be very effective units to improve FFV without detriment of thermal stability or processability [9,[17][18][19].…”