Positronium interactions with gases in pores of silicagels

Goldanskii, V. I.; Mokrushin, A. D.; Tatur, A.O.; Shantarovich, V. P.

doi:10.1007/bf00928028

Cited by 33 publications

(24 citation statements)

References 6 publications

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“…Measurements in contact with air resulted in some shortening of o-Ps lifetimes due to the oxygen quenching, another feature of highly permeable polymers or sorbents. 65 The radii of FV elements in this polymer calculated via the Tao−Eldrup equation are rather similar to those found for PIM-1, especially as concerns R 4 . The R 3 value observed for PIM-EA-TB is smaller than that for the corresponding PIM-1 R 3 .…”

Section: Macromoleculesmentioning

confidence: 80%

Molecular Modeling and Gas Permeation Properties of a Polymer of Intrinsic Microporosity Composed of Ethanoanthracene and Tröger’s Base Units

et al. 2014

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Polymers of intrinsic microporosity (PIMs) are receiving increasing attention from the membrane community because of their high gas and vapor permeability. Recently a novel ethanoanthracene-based PIM synthesized by Troger's base formation (PIM-EA-TB) was reported to have exceptional transport properties, behaving as a polymer molecular sieve membrane. In the present work, an extensive investigation of the structural, mechanical, and transport properties of this polymer, both by experimental analysis and by molecular simulation, offers deep insight into the behavior of this polymer and gives an explanation for its remarkable performance as a membrane material. Transport properties were determined by the barometric time-lag method, by the volumetric method with gas chromatographic or mass spectrometric gas analysis, and by gravimetric sorption measurements, yielding all basic transport parameters, permeability (P), diffusivity (D), and solubility (S). Upon alcohol treatment, PIM-EA-TB exhibited a much stronger permeability increase than archetypal "benchmark" polymer PIM-1, with performance above the Robeson upper bound for several gas pairs. This is in part due to an extremely high gas solubility in PIM-EA-TB, higher than in PIM-1. The experimental data were supported by extensive modeling studies of the polymer structure and the spatial arrangement of its free volume. Modeling confirms that the high gas permeability must be attributed to the large fractional free volume of the polymer. The simulated free volume size distribution in PIM-EA-TB is in agreement with the average experimental free volume elements size determined by PALS and 129 Xe NMR analysis. The modeled spatial arrangement of the free volume revealed a slightly lower interconnectivity of the FV elements in PIM-EA-TB compared to PIM-1. Along with its higher chain rigidity, determined by analysis of the torsion angles in the polymer model, this was identified as the main reason for its stronger size sieving behavior and relatively high permselectivity. A number of peculiarities in the behavior of PIMs will also be discussed here, explaining discrepancies between results published in the literature by different laboratories, the effect of their thermomechanical history, aging, or conditioning, and the influence of the measurement technique and of the experimental conditions on the results. This makes this study of inestimable value for unifying the results of different experimental techniques and fully understanding the transport properties.

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Section: Macromoleculesmentioning

confidence: 80%

Molecular Modeling and Gas Permeation Properties of a Polymer of Intrinsic Microporosity Composed of Ethanoanthracene and Tröger’s Base Units

et al. 2014

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“…The feature of positron annihilation spectra in porous media like silica gels and zeolites is the existence of their very long lifetimes (as long as 70 ns). Thus, according to Goldanskii et al,25 the lifetime of the longest component for silica gel increases with pore diameter. For the minimal pore diameter of 16 A, the time-life reported was equal to 12,000 ps, which is only twice as great as the value r4 found for PTMSP.…”

mentioning

confidence: 90%

Estimation of free volume in poly(trimethylsilyl propyne) by positron annihilation and electrochromism methods

Yampolskii

Shantorovich

Chernyakovskii

et al. 1993

J of Applied Polymer Sci

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SYNOPSISThe free volume of poly( trimethylsilyl propyne) (PTMSP), a glassy polymer distinguished by extremely high gas permeability and diffusion coefficients, was determined by means of two probe techniques-the positron annihilation method and the electrochromism method. Lifetime analysis of positron annihilation spectra revealed an additional long-lived component that is not typical for most of previously studied polymers. A model that has been developed earlier predicts that this lifetime corresponds to the larger size of free-volume elements having an intrinsic radius of about 6 A. Therefore, PTMSP should be similar to porous inorganic sorbents. A comparison with the literary data for zeolites and silica gel confirms this. According to the electrochromism method, the temperature dependence of the size of free-volume elements for PTMSP is much weaker than that for regular glassy polymers like polystyrene. It was concluded that the great free volume in glassy PTMSP is associated with very loose packing of the chains. 0 1993 John Wiley & Sons, Inc. INTRODUCTIONPoly( 1-trimethylsilyl-1-propyne) (PTMSP) synthesis, which has been described by Masuda et al., has drawn great attentionThe gas permeability coefficients ( P ) of PTMSP are at least 1-2 orders of magnitude higher than those of the most permeable synthetic polymers, rubbery or glassy. Additionally, it has been shown that this polymer is characterized by high diffusion coefficients ( D ) , solubility coefficients (S) , and great Langmuir hole saturation constant Ch. This parameter of sorption isotherms is usually considered as a rough measure of the excess free volume in glassy polymers. Interestingly, for this polymer, anomalously low densities have been r e p~r t e d ,~ which for some samples are as low as 0.7 g/cc.It was only natural to explain all these peculiarities as the manifestation of the greater free volume * To whom correspondence should be addressed. of PTMSP. Indeed, it has been assumed that the larger free volume associated with such structural features of glassy PTMSP as the rigid main chain and the bulky Si ( CH3)3 side-chain group is responsible for the observed unusual properties of this p01ymer.~-~ Recently, so-called probe methods have been extensively used to estimate the free volume or characteristic size of its elements in glassy polyrner~.~-~ This work presents the results of the study of PTMSP by means of the positron annihilation method and the electrochromism method. For comparison, two other polymers were studied. The first, poly( vinyl trimethylsilane) (PVTMS) is a vinylictype polymer having the same side-chain group as has PTMSP attached directly to main chain. Transport and thermodynamic properties of PTMSP and PVTMS have been compared earlier.3~'0 The other polymer, polystyrene, was considered as a "typical" glassy polymer whose transport and other physicochemical properties have been extensively studied, including the investigations by means of positron annihilation and electrochromism methods.

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“…Groups working on this problem were encouraged by the unique advantages of this technique, e.g., the ability to characterize closed porosity [1][2][3] or the ability to perform measurements in situ (e.g., at various temperatures [4][5][6][7], mechanical pressures [8] or in the presence of a pore filling gas/liquid [9][10][11][12]). These capabilities are owed to the properties of positronium (Ps), which is used by PALS as a probe of material structure.…”

Section: Introductionmentioning

confidence: 99%

Composition of pore surface investigated by positron annihilation lifetime spectroscopy

Gorgol

Tydda

Kierys

et al. 2012

Microporous and Mesoporous Materials

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Positronium interactions with gases in pores of silicagels

Cited by 33 publications

References 6 publications

Molecular Modeling and Gas Permeation Properties of a Polymer of Intrinsic Microporosity Composed of Ethanoanthracene and Tröger’s Base Units

Molecular Modeling and Gas Permeation Properties of a Polymer of Intrinsic Microporosity Composed of Ethanoanthracene and Tröger’s Base Units

Estimation of free volume in poly(trimethylsilyl propyne) by positron annihilation and electrochromism methods

Composition of pore surface investigated by positron annihilation lifetime spectroscopy

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