A combined atomic and molecular probe characterization of aromatic hydrocarbons via PALS and ESR: methylbenzene

0552529 - ÚMCH 2023 RIV CH eng J - Journal Article
Bartoš, J. - Zgardzińska, B. - Švajdlenková, H. - Charmas, B. - Lukešová, Miroslava - Wysoglad, K. - Goździuk, M.
A combined atomic and molecular probe characterization of aromatic hydrocarbons via PALS and ESR: methylbenzene.
Materials. Roč. 15, č. 2 (2022), č. článku 462. E-ISSN 1996-1944
Institutional support: RVO:61389013
Keywords : methylbenzene or toluene * positronium * free volume
OECD category: Polymer science
Impact factor: 3.4, year: 2022
Method of publishing: Open access
https://www.mdpi.com/1996-1944/15/2/462

A combined study of one of the simplest aromatic hydrocarbons, i.e., methylbenzene (toluene) (TOL), via the annihilation of an ortho-positronium (o-Ps) probe via positron annihilation lifetime spectroscopy (PALS) and the rotation dynamics of nitroxide spin probe 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) using electron spin resonance (ESR) over a wide temperature range, 10–300 K, is reported. The o-Ps lifetime, τ3, and the relative o-Ps intensity, I3, as a function of temperature exhibit changes defining several characteristic PALS temperatures in the slowly and rapidly cooled samples. Similarly, the spectral parameter of TEMPO mobility in TOL, 2Azz‘, and its correlation time, τc, reveal several effects at a set of the characteristic ESR temperatures, which were determined and compared with the PALS results. Finally, the physical origins of the changes in free volume expansion and spin probe mobility are revealed. They are reflected in a series of the mutual coincidences between the characteristic PALS and ESR temperatures and appropriate complementary thermodynamic and dynamic techniques.
Permanent Link: http://hdl.handle.net/11104/0327799