Gas transport and free volume in hexafluoropropylene polymers

Белов, Н. А.; Жаров, А. А.; Shashkin, A. V.; Shaikh, M.Q.; Raetzke, K.; Yampolskii, Yu. P.

doi:10.1016/j.memsci.2011.08.029

Cited by 52 publications

(27 citation statements)

References 30 publications

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“…Free volume features, including size distribution and connectivity, were considered as key parameters determining gas transport performance [ 38 , 39 ]. Molecular simulations were conducted to study the free volume.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Molecular Isomerism on the Barrier Properties of Polyimides: Perspectives from Experiments and Simulations

et al. 2021

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A novel carbazole-containing diamine (M-2,7-CPDA) isomer of our previously reported diamine 2,7-CPDA, has been synthesized using a two-step synthesis. Compared with 2,7-CPDA, the substituted position of amino is changed from para to meta for M-2,7-CPDA. The two diamines were polymerized with pyromellitic dianhydride (PMDA) to prepare two isomeric polyimides (M-2,7-CPPI and 2,7-CPPI), respectively. The effects of para/meta isomerism on microstructures and gas barrier performances of the two isomeric polyimides were studied by positron annihilation test, X-ray diffraction and molecular simulation. The results display that meta-connected M-2,7-CPPI has less ordered chain structure and weaker hydrogen bonding than para-connected 2,7-CPPI, which leads to loose chain stacking and thereby increased free volumes of M-2,7-CPPI. The higher free volumes promote the solubility and diffusivity of gas in M-2,7-CPPI. As a result, the meta-linked M-2,7-CPPI shows a lower gas barrier than its para-linked analog. The work provides guidance for the design and synthesis of high-performance barrier polymers.

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Section: Resultsmentioning

confidence: 99%

The Effect of Molecular Isomerism on the Barrier Properties of Polyimides: Perspectives from Experiments and Simulations

et al. 2021

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“…It seems that the rigid molecular chain packing in NPGD-230 membrane creates less diffusion channels for CO 2 gas molecules. In order to gain further insight into the effect of molecular chain packing on the CO 2 gas transport, we analyzed the free volume holes in the membrane microstructure, where the gas molecules are considered to jump for diffusion [10,11]. The free volume parameters (o-Ps lifetime, distribution and intensity) measured by PALS are reported in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Gas transport and free volume study in polyethylene based epoxy membranes

Patil

Checchetto

Ferragut

et al. 2015

J. Phys.: Conf. Ser.

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Abstract. The mechanism of gas diffusivity in amine modified epoxy membranes is studied in the frame of free volume properties. Epoxy membranes with two different crosslinking densities and composite with Graphene nanoplatelets were prepared by solvent casting method. The free volume parameters measured by Positron Annihilation Spectroscopy (PAS) show inverse correlation with crosslinking density of the samples. The gas permeability and diffusivity for CO 2 have been studied by gas permeation measurements. The study reveals that the gas permeability and diffusivity change significantly as a function of crosslinking density, free volumes and structural relaxations of the molecular chains.

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“…The synthesis, kinetics, and mechanism of polymerization of PHFP have been described previously in detail . Gas permeation properties, a free‐volume study by PALS, and vapor sorption characterization were also performed . The average viscosity molecular mass of the polymer was as high as 1 × 10 6 Da.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The transport parameters at 25 ± 3°C for He, O 2 , N 2 , and CO 2 were measured using a mass spectrometric technique and barometric techniques on a Balzers QMG 420 quadrupole mass spectrometer (Liechtenstein, Balzers) and an MKS Barotron(MKS, Instruments Deutschland GmbH, Germany Munich), respectively. The upstream pressure was 0.8–0.95 atm, and the downstream pressure was about 10 −3 mm Hg for the spectrometric method, while for the barometric technique tha pressure was in the range of 0.1–1 mm Hg; therefore, the reverse diffusion of penetrating gas was negligible.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Microstructure relaxation process of polyhexafluoropropylene after swelling in supercritical carbon dioxide

Белов

Alentiev

Ronova

et al. 2015

J of Applied Polymer Sci

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This paper studies the process of relaxation of a polymer after swelling in supercritical carbon dioxide. Polyhexafluoropropylene (PHFP) was chosen as the object for investigation. The relaxation process was monitored by a change of the permeability coefficients for a number of gases. Thin polymeric films of PHFP were modified by different treatments: drying to a constant weight, annealing at a temperature slightly higher than the glass-transition temperature, and swelling in supercritical carbon dioxide. The permeability coefficients of six gases, He, H 2 , O 2 N 2, CO 2 , and CH 4 , were measured after each stage of the treatment. It was shown that the permeability coefficients in the films were increased by 2.4 times for He, 3.6 for H 2 , 5.9 for O 2 , 8.1 for N 2 , 6.7 for CO 2 , and 10.9 for methane. The permeability coefficients of the same gases were measured 50 days later after swelling in supercritical carbon dioxide. A decrease in the permeability coefficient demonstrated that the relaxation process had taken place. Nevertheless, the values exceeded the initial ones for annealed samples by 2.0 times for He, 2.4 for H 2 , 1.8 for O 2 , 1.7 for N 2 , 1.7 for CO 2 , and 1.3 for methane.

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Gas transport and free volume in hexafluoropropylene polymers

Cited by 52 publications

References 30 publications

The Effect of Molecular Isomerism on the Barrier Properties of Polyimides: Perspectives from Experiments and Simulations

The Effect of Molecular Isomerism on the Barrier Properties of Polyimides: Perspectives from Experiments and Simulations

Gas transport and free volume study in polyethylene based epoxy membranes

Microstructure relaxation process of polyhexafluoropropylene after swelling in supercritical carbon dioxide

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