Gas permeability and selectivity of hexafluoroisopropylidene aromatic isophthalic copolyamides

Abstract

The synthesis, thermal, and gas transport properties of poly(hexafluoroisopropylidene isophthalamide), HFA/ISO homopolymer, and HFA/TERT‐co‐HFA/ISO copolyamides with different poly(hexafluoroisopropilydene‐5‐t‐butylisophthalamide), HFA/TERT, ratios are reported. The results indicate that the glass transition temperatures of the copolyamides increase as the concentration of HFA/TERT in the polyamide increases. The gas permeability coefficients in the polyamides and copolyamides are independent of pressure or decrease slightly particularly with CO2, N2, and CH4. It was seen that HFA/TERT is 2–6 times more permeable than HFA/ISO, depending on the gas being considered. This was assigned to the presence of the bulky lateral substituent, t‐butyl group in HFA/TERT and HFA/TERT‐co‐HFA/ISO copolyamides. This substituent increases fractional free‐volume, as expected. Therefore, the gas permeability and diffusion coefficients generally increase with increasing fractional free‐volume. The experimental results for the gas permeability and permselectivity for the copolyamides was well represented by a logarithmic mixing rule of the homopolyamides permeability coefficients and their volume fraction. The selectivity of gas pairs, such as O2/N2, CO2/CH4, and N2/CH4 decreased slightly with the addition of HFA/TERT. The temperature dependence of permeability for homopolyamides and copolyamides can be described by an Arrhenius type equation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2625–2638, 2005

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.…”

“…The experimental studies of aromatic polyamides based on 4,4 0 -hexafluoroisopropylidene diamine (HFA) showed a relationship between the density and the gas transport properties as result of the addition of different concentrations of pendant groups in the diacid monomer. [5] These published densities can be used to validate MD simulation method used here, which also can be used to compute densities of new aromatic polyamides without having to synthesize them. The seven structures used for this study and its acronyms are given in Figure 1.…”

The effect of fluorine atoms on gas transport properties of new polynorbornene dicarboximides

“…For example, poly(Nadamantyl-norbornene-5,6-dicarboximide) (P-AdNDI) showed a T g of 271 8C [6]. Even though polynorbornene dicarboximides, such as P-AdNDI, have bulky pendant groups, their gas permeability coefficients are not high but similar to those of amorphous polyesters or polyamides [7][8][9]. It is well known, that in many cases higher permeabilities are found for glassy polymers with higher glass transition temperature [10][11][12].…”

Preparation and characterization of cellulose nanocomposite films with two different organo-micas

“…There are two main factors in the permeability reduction, namely the polymer chain-segment immobility and the detour ratio, which is defined as the ratio of the film thickness in the nominal diffusion flow direction to the average length of the tortuous diffusion distance between the clay layers (Chaiko and Leyva 2005;Cristian and Manuel 2005;Xu et al 2006;Zoppi et al 2000).…”