Gas permeability and selectivity of benzophenone aromatic isophthalic copolyamides

Abstract

The synthesis, thermal, and gas transport properties of poly(benzophenone isophthalamide), DBF/ISO, poly(benzophenone‐5‐tert‐butylisophthalamide), DBF/TERT, homopolymers, and their copolyamides with different DBF/TERT ratios are reported. The results indicate that the glass transition temperatures of the copolyamides increase as the concentration of DBF/TERT in the polyamide increases. The gas permeability coefficients for DBF/ISO are around 10−2 Barrers for O2 which situates this polymer as a barrier polymer. It was also found that permeability coefficients in all polyamides and copolyamides are independent of pressure for He or decrease slightly particularly with O2, CO2, and N2. It was seen that DBF/TERT is up to 15 times more permeable than DBF/ISO, depending on the gas being considered. This behavior was assigned to the presence of the bulky lateral substituent, the tert‐butyl group, in DBF/TERT and DBF/TERT‐co‐DBF/ISO copolyamides. This bulky substituent increases fractional free volume and interchain spacing; as a consequence, the gas permeability and diffusion coefficients generally increase. The experimental results for the gas permeability coefficients and permselectivity for the copolyamides was well represented by a semilogarithmic mixing rule of the homopolyamides permeability coefficients as a function of their volume fraction. The selectivity of gas pairs, such as He/O2 and He/CO2, decreased slightly with the addition of DBF/TERT. The temperature dependence of permeability for homopolyamides and copolyamides can be described by an Arrhenius type equation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2083–2096, 2007

Synthesis, Characterization, and Gas Transport Properties of New Copoly(ether-Amide)s Containing Benzophenone Aromatic Isophthalic Segment

“…Permeability and selectivity may be governed by either kinetic (D) or thermodynamic (S) parameters or both 25,26 . As shown in Table 3 the gas diffusion coefficients follow the order , similar behavior has been observed for DBFISO polyamide membranes and in general for amorphous polymers 19 . The CO 2 diffusion coefficient seems to be identical in the three copoly(ether-amide) membranes and increasing slightly with increasing length of the polyether block.…”

“…Table 2 shows the pure gas permeability coefficients, P, for the copoly(ether-amide) membranes evaluated at 35 °C and 10 atm. In general, all copoly(ether-amide)s show gas permeability coefficients values that are one order of magnitude higher than those presented by the DBFISO polyamide 19 with the exception of He that presents P values of the same order of magnitude. The DI400 copoly(ether-amide) membrane, with the shortest polyether block content and segment shows the highest CO 2 permeability coefficient and the highest ideal selectivity for the pairs CO 2 /N 2 , CO 2 /CH 4 , and CO 2 /O 2 .…”

“…Membranes prepared from DBFISO aromatic polyamides have been reported to present low gas permeability coefficients that classifies them as gas barrier polymers 19 . Owing to the polarity introduced by the incorporation of soft polyether block segments in the polyamide backbone, the three copoly(etheramide) membranes synthesized are more permeable than convenctional DBFISO aromatic polyamides 8,15 .…”

Synthesis and gas transport properties of rigid block copolyaramides

“…The separation of gases by membranes has been studied for some time now; however, there are still interests in developing materials that present high gas permeability and high selectivity to specific gas pairs at the same time to effect their separation [7][8][9][10][11][12][13]. The relationship between the polymer structure and their gas transport properties has been studied systematically for several highly aromatic rigid polymers such as polyesters [9,14,15], polysulfones [16][17][18], polycarbonates [18,19], polyimides [20], polyamides [7,8,10,21], polynorbornene dicarboxyimides [22,23].…”

“…The main reason is that copolymer synthesis offers the ability to tailor the properties of a polymeric material in a desired direction by the introduction of an appropriately chosen second or in some cases a third monomeric unit sequence, allowing us to alter such polymer properties as flexibility, crystallinity, thermal stability, glass transition temperature and gas transport [1][2][3][4][5][6][7][8][9].…”