Positron Annihilation Lifetime Spectroscopy (PALS) for Interdiffusion Studies in Disperse Blends of Compatible Polymers:  A Quantitative Analysis

Dlubek, G.; Pionteck, Jürgen; Бондаренко, В. А.; Pompe, G.; Taesler, Ch.; Petters, K.; Krause‐Rehberg, R.

doi:10.1021/ma020451z

Cited by 39 publications

(49 citation statements)

References 39 publications

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“…We have shown that the o-Ps intensity I 3 , which mirrors the Ps yield, depends on whether Ps inhibitors are distributed throughout a material homogeneously or heterogeneously. This effect can be used to study the interdiffusion in an originally demixed blend of two miscible polymers [Dlubek et al, 2002c] or the opposite process, the demixing of originally mixed polymers [Günther-Schade et al, 2002].…”

Section: Discussionmentioning

confidence: 99%

Local Free‐Volume Distribution from PALS and Dynamics of Polymers

Dlubek

2010

Polymer Physics

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Section: Discussionmentioning

confidence: 99%

Local Free‐Volume Distribution from PALS and Dynamics of Polymers

Dlubek

2010

Polymer Physics

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“…The o-Ps intensity I 3 , which mirrors the Ps yield, depends on whether inhibitors for the Ps formation are homogeneously or heterogeneously distributed in a material (163)(164)(165). This effect can be used to study the interdiffusion in an originally demixed blend of two miscible polymers.…”

Section: Positron Annihilation As a Chemical Probe For Polymersmentioning

confidence: 99%

Positron Annihilation Spectroscopy

Dlubek

2008

Encyclopedia of Polymer Science and Technology

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FundamentalsThe positron is the antiparticle of the electron, ie, it has the opposite charge but otherwise the same properties. In matter, a positron may be created either by the β + decay of an unstable nucleus or from a high-energy γ-photon via e + -e − pair production. If the positron encounters an electron, both particles annihilate, ie, they are transformed into photons of an energy, which is given by the famous Einstein equation, E = 2mc 2 . Here, m is the mass of the electron, c the speed of light in vacuum, and for particles at rest E = 2 × 0.511 MeV. The selection rules for the γ-photon emission are derived from the conservation laws of energy and momentum and parity considerations. Free positrons annihilate mainly into two γ-photons of energy 0.511 MeV emitted in almost collinear directions, or with much less probability into three photons of an overall energy of 1.022 MeV (16,24,25).In nonconducting materials, such as polymers, positrons can exist as free particles (e + ) or as positronium (Ps, e + e − ), which is a positron-electron bound state. Ps was experimentally discovered by DeBenedetti and Richings in 1952 (26). The "chemical" symbol Ps for positronium appears to have been introduced by McGervey and DeBenedetti in 1959 (27). Its properties and interaction with matter were reviewed in several articles (25-30). Ps is a particle of the size of a hydrogen atom, r Ps = 0.53Å, but only the mass of two electrons, and a binding energy of 6.8 eV, that is half of the ionization energy of hydrogen. The lifetime of a Ps atom depends on the relative spin orientation of positron and electron. The para-Ps (p-Ps, singlet state, spins antiparallel) decays into two photons with a mean intrinsic lifetime (self-annihilation in a vacuum) of τ pPs 0 = 0.125 ns. The ortho-Ps (o-Ps, triplet state, spins parallel) can decay only into three photons, a much slower process than two-photon emission. Therefore, o-Ps has an intrinsic lifetime of τ oPs 0 = 142 ns. The formation probabilities of the p-Ps and o-Ps states are 0.25 and 0.75 of the total Ps yield (16,25).In condensed matter studies, 22 Na is usually used as the positron source. This isotope has a half-life of 2.6 years and emits positrons with an energy distribution that has its maximum at 0.20 MeV and ranges up to 0.54 MeV (10,16). The stopping profile of positrons is a decreasing exponential function. In materials with a density of 1 g/cm 3 50%, 90%, and 99% of positrons are stopped within a thickness of 0.170, 0.60, and 1.20 mm, respectively. The energetic positrons lose their energy rapidly via ionization and excitation of electrons and finally phonons. After a few picoseconds, the positrons are in thermal equilibrium with the ambient material. In defect-free molecular crystals, positrons migrate over a mean distance of typically 100 nm before annihilating. In defected crystals and in amorphous matter, positrons may annihilate from local free volumes. The mean positron lifetimes are typically τ e+ = 200-400 ps.

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“…We find several studies reported on the interfacial properties in terms of interdiffusion at the interface, [22][23][24][25][26] interfacial tension, [27][28][29][30] and interface width, 21,[31][32][33][34] and so forth in polymer blends. The magnitude and behavior of interface width with varying molecular weight, temperature, and film thickness have also been studied using the small angle neutron scattering, neutron reflectometry, 27,28,[33][34][35] small angle X-ray scattering, differential scanning calorimetry (DSC), 26 transmission electron microscopy, 30 and so forth with varying success.…”

Section: Introductionmentioning

confidence: 92%

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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Positron Annihilation Lifetime Spectroscopy (PALS) for Interdiffusion Studies in Disperse Blends of Compatible Polymers: A Quantitative Analysis

Cited by 39 publications

References 39 publications

Local Free‐Volume Distribution from PALS and Dynamics of Polymers

Local Free‐Volume Distribution from PALS and Dynamics of Polymers

Positron Annihilation Spectroscopy

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

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