Positron annihilation spectroscopy studies of implanted polymer membranes

Constantin, F.; Petruneac, Marta; Focşǎneanu, Marin

doi:10.1002/pat.5079

Cited by 2 publications

(2 citation statements)

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“…Polyethylene and Nafion membranes implanted by Cu ions at various fluences (up to 10 17 ions/cm 2 ) were studied using two positron techniques: lifetime and coincidence Doppler broadening (CBD) [ 77 ]. Although the polyethylene spectrum is more complex, due to the presence of a Ps component localized in the crystalline zones, in the amorphous phase (predominant in Nafion), the behavior of Ps is similar in the two membranes: at low implantation doses, the free volume holes shrink, which is interpreted by the authors in terms of crosslinking and aggregation of ions in metallic microstructures.…”

Section: Discussion Of Some Pals Results In Polymeric Systemsmentioning

confidence: 99%

“…The results are similar to those found in the study concerning the per-fluorinated sulfonic acid/PTFE proton exchange membranes, already quoted [73], with analogous interpretation: the decrease in the free volume holes is explained in terms of occupancy of the intermolecular spaces by water molecules. Higher water uptake involves a strong bonding between the water molecules Polyethylene and Nafion membranes implanted by Cu ions at various fluences (up to 10 17 ions/cm 2 ) were studied using two positron techniques: lifetime and coincidence Doppler broadening (CBD) [77]. Although the polyethylene spectrum is more complex, due to the presence of a Ps component localized in the crystalline zones, in the amorphous phase (predominant in Nafion), the behavior of Ps is similar in the two membranes: at low implantation doses, the free volume holes shrink, which is interpreted by the authors in terms of crosslinking and aggregation of ions in metallic microstructures.…”

Section: Membranesmentioning

confidence: 99%

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Probing the Free Volume in Polymers by Means of Positron Annihilation Lifetime Spectroscopy

Consolati

Nichetti²,

Quasso

2023

Polymers

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Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10−7. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials.

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Section: Discussion Of Some Pals Results In Polymeric Systemsmentioning

confidence: 99%

Section: Membranesmentioning

confidence: 99%