Erratum: Positronium annihilation in molecular substances [J. Chem. Phys. <b>5</b>
                  <b>6</b>, 5499 (1972)]

Tao, S. J.

doi:10.1063/1.441776

Cited by 338 publications

(463 citation statements)

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“…The o-Ps lifetime is sensitive to both the electron density in the neighbourhood of the Ps and to the free-volume hole size [2][3][4][5][6][7]. For an o-Ps confined in an infinitely deep potential well the semiempirical Tao-Eldrup model and its extensions [8][9][10][11][12] establish a correlation between the free-volume hole radius, R, and the o-Ps pick-off lifetime, τ o−Ps , giv-…”

Section: Introductionmentioning

confidence: 99%

Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

et al. 2008

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Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the CO 2 gas permeability through the membranes.

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Section: Introductionmentioning

confidence: 99%

Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

et al. 2008

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“…The longest lived components s 3 with intensity I 3 is due to pick-off annihilation of the o-Ps from the free volume sites present mainly in the amorphous regions of the polymer matrix. Nakanishi et al, 46 relation based on Tao 47 and Eldrup et al 48 work is used to calculate the free volume cell radius (R) from the measured s 3 (o-Ps lifetime).…”

Section: Positron Annihilation Lifetime Measurementsmentioning

confidence: 99%

A new insight into interface widths in binary polymer blends based on ortho‐positronium lifetime studies

Ramya

Ranganathaiah

2012

J of Applied Polymer Sci

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The interface widths in two immiscible polymer blend (Poly vinyl chloride (PVC)/Polystyrene (PS)) and PVC/Ethylene Vinyl Acetate (EVA) are determined experimentally using hydrodynamic interaction approach through free volume measurement by positron annihilation lifetime spectroscopy. For comparison, the same study is performed in a miscible blend (Styrene Acrylonitrile (SAN)/Poly Methyl Methacrylate (PMMA)). The interfacial width (Dl) is evaluated from the hydrodynamic interaction (a) based on Kirkwood-Risemann theory and friction coefficient from Stokes equation. Friction at the interface of a binary blend evidences how close the surfaces of the polymer chains come or stay apart which in turn depends on the type of force/interaction at the interface. In this work, we define interface width from a different perspective of Flory-Huggins interaction approach. Measured composition dependent interface widths in the three blends studied clearly demonstrate the sensitivity of the present method. In miscible blend, high friction at the interface results in stronger hydrodynamic interaction and hence smaller interface widths (0.36-1.97 Å ), whereas weak or no interaction in immiscible blends produce wider widths (2.81-25.0 Å ).

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“…The mean radius of the free-volume holes can be roughly estimated by means of a simple quantum-mechanical model, [53][54][55] where the o-Ps in a free-volume hole is approximated to a particle in an infinite spherical potential well of radius R o . The o-Ps lifetime (s 3 ) localized in a free-volume hole is related to its hole (assumed spherical) radius (R) as…”

Section: Full Papermentioning

confidence: 99%

Hierarchical Porosity in Self‐Assembled Polymers: Post‐Modification of Block Copolymer–Phenolic Resin Complexes by Pyrolysis Allows the Control of Micro‐ and Mesoporosity

Valkama¹,

Nykänen²,

Kosonen³

et al. 2006

Adv Funct Materials

105

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It is shown that self‐assembled hierarchical porosity in organic polymers can be obtained in a facile manner based on pyrolyzed block‐copolymer–phenolic resin nanocomposites and that a given starting composition can be post‐modified in a wide range from monomodal mesoporous materials to hierarchical micro‐mesoporous materials with a high density of pores and large surface area per volume unit (up to 500–600 m2 g–1). For that purpose, self‐assembled cured composites are used where phenolic resin is templated by a diblock copolymer poly(4‐vinylpyridine)‐block‐polystyrene (P4VP‐b‐PS). Mild pyrolysis conditions lead only to monomodal mesoscale porosity, as essentially only the PS block is removed (length scale of tens of nanometers), whereas during more severe conditions under prolonged isothermal pyrolysis at 420 °C the P4VP chains within the phenolic matrix are also removed, leading to additional microporosity (sub‐nanometer length scale). The porosity is analyzed using transmission electron microscopy (TEM), small‐angle X‐ray scattering, electron microscopy tomography (3D‐TEM), positron annihilation lifetime spectroscopy (PALS), and surface‐area Brunauer–Emmett–Teller (BET) measurements. Furthermore, the relative amount of micro‐ and mesopores can be tuned in situ by post modification. As controlled pyrolysis leaves phenolic hydroxyl groups at the pore walls and the thermoset resin‐based materials can be easily molded into a desired shape, it is expected that such materials could be useful for sensors, separation materials, filters, and templates for catalysis.

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Erratum: Positronium annihilation in molecular substances [J. Chem. Phys. 5 6, 5499 (1972)]

Cited by 338 publications

References 0 publications

Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

A new insight into interface widths in binary polymer blends based on ortho‐positronium lifetime studies

Hierarchical Porosity in Self‐Assembled Polymers: Post‐Modification of Block Copolymer–Phenolic Resin Complexes by Pyrolysis Allows the Control of Micro‐ and Mesoporosity

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