Gas separation properties of aromatic polyamides containing hexafluoroisopropylidene groups

Aromatic Polyamides Density from Molecular Dynamics Simulation

“…The density reported for HFAISO and HFATERT are experimental 1.422/1.411 MD calculation and experimental 1.305/1.304 g/cm 3 MD simulation, respectively. [5,7] Therefore, these results validate that the MD simulation method is a relatively effective method to predict densities on this type of aromatic polyamides. On the basis of these data, we employed MD simulations to evaluate densities of other aromatic polyamides, which have different pendant groups on the diacid monomer moiety.…”

“…[9] At this point, the calculated density data were used to evaluate chain packaging by calculating the fractional free volume (FFV c ), which was estimated using the following relation: FFV c ¼ (V sp -1:3V VACB vdW )/V sp , where V sp is the polymer specific volume and V vdW is the van der Waals volume of a structural unit, which was calculated using the method atomic and bond contributions of van der Waals volume (VACB). [10] Moreover, FFV has been also determined using the following relation: [5] and Morisato et al, [7] have reported FFV values for HFAISO and HFATERT by using van der Waals volume obtained from Bondi´s group contribution method. Their FFV results are higher than those obtained in this work.…”

Spiro[fluorene-9,9′-xanthene] containing fluorinated poly(ether amide)s: Synthesis, characterization and gas transport properties

“…Actually, cardo fluorene moiety into the polymer backbone hinders the intermolecular interaction of the polymer repeat units as well as increases the rigidity of main chains. The incorporation of fluorine in the form of ACF 3 or hexafluoroisopropylidene groups in the polymer backbone breaks the symmetry of the polymer and introduces significant chain separation and rigidity and thereby improving their solubility, electrical insulating properties, gas permeability and permselectivity, flame resistance, environmental stability, and optical transparency, dielectric and physical properties [5,[8][9][10][11][12]15,17,18,31]. The fluorinated polymeric membranes showed low tendency of plasticization in the gas permeation.…”

“…Therefore, research efforts are directed toward the reduction of this interchain packing by inhibiting hydrogen bonding between amide linkages in polyamides, thus increasing the free volume, to yield materials with superior solubility (processability) and improved gas permeability. Incorporation of specific groups into the polyamide backbones leads to high performance polymeric materials that exhibit certain valuable properties, such as electrochromic, gas separation, charge-transporting, highly refractive and photosensitive properties [10,17,[18][19][20][21]. Considerable efforts have been made to increase the processability and solubility of aramids by structural modification without compromising their chemical, thermal, and mechanical properties so that applicability of aromatic PAs is expanded and remains on the forefront of scientific research.…”

“…Despite these interesting properties of polyamides, in literature gas separation membrane based study on this class of polymer is scarcely found. Since polyamides commonly have high cohesive energy density and show a tendency for very efficient polymer chain packing along with rigid polymer backbone, they normally exhibit poor processability and low gas permeability [17,18]. Therefore, research efforts are directed toward the reduction of this interchain packing by inhibiting hydrogen bonding between amide linkages in polyamides, thus increasing the free volume, to yield materials with superior solubility (processability) and improved gas permeability.…”