scholarly journals On the Mutual Relationships between Molecular Probe Mobility and Free Volume and Polymer Dynamics in Organic Glass Formers: cis-1,4-poly(isoprene)

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 294
Author(s):  
Helena Švajdlenková ◽  
Ondrej Šauša ◽  
Sergey V. Adichtchev ◽  
Nikolay V. Surovtsev ◽  
Vladimir N. Novikov ◽  
...  
Keyword(s):  
Free Volume ◽  
Spin Probe ◽  
Hyperfine Coupling Constant ◽  
Organic Glass ◽  
Molecular Probe ◽  
Positron Annihilation Lifetime ◽  
Broadband Dielectric Spectroscopy ◽  
Relaxation Modes ◽  
Reorientation Dynamics ◽  
In Cis

We report on the reorientation dynamics of small spin probe 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) in cis-1,4-poly(isoprene) (cis-1,4-PIP10k) from electron spin resonance (ESR) and the free volume of cis-1,4-PIP10k from positron annihilation lifetime spectroscopy (PALS) in relation to the high-frequency relaxations of cis-1,4-PIP10k using light scattering (LS) as well as to the slow and fast processes from broadband dielectric spectroscopy (BDS) and neutron scattering (NS). The hyperfine coupling constant, 2Azz′(T), and the correlation times, τc(T), of cis-1,4-PIP10k/TEMPO system as a function of temperature exhibit several regions of the distinct spin probe TEMPO dynamics over a wide temperature range from 100 K up to 350 K. The characteristic ESR temperatures of changes in the spin probe dynamics in cis-1,4-PIP10k/TEMPO system are closely related to the characteristic PALS ones reflecting changes in the free volume expansion from PALS measurement. Finally, the time scales of the slow and fast dynamics of TEMPO in cis-1,4-PIP10k are compared with all of the six known slow and fast relaxation modes from BDS, LS and NS techniques with the aim to discuss the controlling factors of the spin probe reorientation mobility in polymer, oligomer and small molecular organic glass-formers.

Dynamic and free volume aspects of spin probe TEMPO in organic glass formers: Polymer cis-1,4-poly(isoprene)

2018 ◽  
Author(s):  
Helena Švajdlenková ◽  
Ondrej Šauša ◽  
Katarína Čechová ◽  
Josef Bartoš
Keyword(s):  
Free Volume ◽  
Spin Probe ◽  
Organic Glass

Molecular probe dynamics and free volume in organic glass-formers and their relationships to structural relaxation: 1-propanol

2015 ◽  
Vol 28 (1) ◽  
pp. 015101 ◽  
Author(s):  
J Bartoš ◽  
H Švajdlenková ◽  
O Šauša ◽  
M Lukešová ◽  
D Ehlers ◽  
...  
Keyword(s):  
Free Volume ◽  
Structural Relaxation ◽  
Organic Glass ◽  
Molecular Probe

scholarly journals A Combined Atomic and Molecular Probe Characterization of Aromatic Hydrocarbons via PALS and ESR: Methylbenzene

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 462
Author(s):  
Josef Bartoš ◽  
Bożena Zgardzińska ◽  
Helena Švajdlenková ◽  
Barbara Charmas ◽  
Miroslava Lukešová ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Aromatic Hydrocarbons ◽  
Volume Expansion ◽  
Spin Probe ◽  
Molecular Probe ◽  
Positron Annihilation Lifetime ◽  
Spin Resonance ◽  
Dynamic Techniques

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.

scholarly journals Molecular probe dynamics and free volume heterogeneities in n-propanol confined in a regular MCM-41 matrix by ESR and PALS

RSC Advances ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 2283-2294 ◽  
Author(s):  
Josef Bartoš ◽  
Helena Švajdlenková ◽  
Ondrej Šauša
Keyword(s):  
Free Volume ◽  
Spin Probe ◽  
Molecular Probe ◽  
Mcm 41

A combined investigation of the spin probe TEMPO mobility and the free volume holes in n-propanol (n-PrOH) confined in a regular virgin MCM-41 matrix by means of ESR or PALS techniques, respectively, is reported.

scholarly journals Shape and Temperature Expansion of Free Volume Holes in Some Cured Polybutadiene-Polyisoprene Rubber Blends

2021 ◽  
Vol 22 (3) ◽  
pp. 1436
Author(s):  
Giovanni Consolati ◽  
Eros Mossini ◽  
Dario Nichetti ◽  
Fiorenza Quasso ◽  
Giuseppe Maria Viola ◽  
...  
Keyword(s):  
Free Volume ◽  
Radial Direction ◽  
Volume Fraction ◽  
Spherical Shape ◽  
Suitable Model ◽  
Positron Annihilation Lifetime ◽  
Rubber Blends ◽  
Free Volume Fraction ◽  
Hole Model ◽  
Best Fit

The free volume fraction of a macromolecular structure can be assessed theoretically by using a suitable model; however, it can also be evaluated from experimental data obtained from dilatometry and positron annihilation lifetime spectra. In this second case, a regular geometry of the sub-nanometric cavities forming the free volume has to be assumed, although in fact they are irregularly shaped. The most popular approach is to guess spherical holes, which implies an isotropic growth of these last with temperature. In this work, we compared the free volume fraction, as obtained from experiments in a set of polybutadiene and polyisoprene cured rubbers and their blends, with the analogous quantity expected by using the lattice-hole model. The results allowed us to obtain insights on the approximate shape of the holes. Indeed, a cylindrical flattened geometry of the cavities produced a better agreement with the theory than the spherical shape. Furthermore, the best fit was obtained for holes that expanded preferentially in the radial direction, with a consequent decrease of the aspect ratio with temperature.

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

Ceramide increases free volume voids in DPPC membranes

RSC Advances ◽  
2015 ◽  
Vol 5 (55) ◽  
pp. 44282-44290 ◽  
Author(s):  
E. Axpe ◽  
A. B. García-Arribas ◽  
J. I. Mujika ◽  
D. Mérida ◽  
A. Alonso ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Lipid Membranes ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime

We have measured by positron annihilation lifetime spectroscopy (PALS) that ceramide increases the size of the free volume holes in DPPC lipid membranes.

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