Thermodynamic and Dynamic Transitions and Interaction Aspects in Reorientation Dynamics of in : A Series of with .

The spectral and dynamic properties of in a series of ranging from to over a temperature range 100-300 K were investigated by ). The main characteristic ESR temperatures connected with slow to fast motion regime transition; 's and 's are situated above the corresponding glass temperatures, , and for the the 's lie above or close to melting point, , while the the < relationship indicates that the are in the local disordered regions of the . The 's and especially 's are compared with the dynamic crossover temperatures, = 8.

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

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.

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

We report on the reorientation dynamics of small spin probe 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) in -1,4-poly(isoprene) (-1,4-PIP10k) from electron spin resonance (ESR) and the free volume of -1,4-PIP10k from positron annihilation lifetime spectroscopy (PALS) in relation to the high-frequency relaxations of -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, 2'(), and the correlation times, (), of -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 -1,4-PIP10k/TEMPO system are closely related to the characteristic PALS ones reflecting changes in the free volume expansion from PALS measurement.

Dynamics of Confined Short-Chain in by Dielectric Spectroscopy: Effects of and Treatments and Filling Factor.

The dynamics of confined in regular with the pore size = 40 Å, under various matrix conditioning and sample confining conditions, using broadband dielectric spectroscopy (BDS), is reported. First, various drying procedures with the capacitor filling under or influence the BDS spectra of the empty and the confined , but have a little effect on the maximum relaxation time of the main process. Finally, various filling factors of in the optimally treated lead to unimodal or bimodal spectra interpreted in terms of the two dynamic phases in the confined states.

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

A combined investigation of the spin probe TEMPO mobility and the free volume holes in -propanol (-PrOH) confined in a regular virgin MCM-41 matrix by means of ESR or PALS techniques, respectively, is reported. Dynamics of spin probe TEMPO alters at several characteristic ESR temperatures which are close to the characteristic PALS ones reflecting the changes in -Ps annihilation and the related free volume. Correlations between these characteristic ESR and PALS temperatures indicate the common physical origins of the respective changes in the free volume expansion and the TEMPO mobility in the confined liquid -PrOH.

ESR evidence of the dynamic crossover in the supercooled liquid states of a series of solid n-alkanes.

A study of the rotation dynamics of the spin probe TEMPO by electron spin resonance (ESR) spectroscopy in a series of six short- and medium-sized n-alkanes is presented. In addition to the usual crossover effects connected with solid-liquid phase transitions at temperature Tm and the solid-solid transition at Tss, we find a strong correlation between the change in reorientation at the characteristic ESR temperature TfastX1 < Tss and/or Tm with the ratio TfastX1/Tm = 0.76 ± 0.

The free-volume structure of a polymer melt, poly(vinyl methylether) from molecular dynamics simulations and cavity analysis.

In this work we analyze and compare the free volume of a polymer system poly(vinyl methylether) (PVME) at 300 K obtained by the two direct but different approaches: Positron annihilation lifetime spectroscopy (PALS) and computer simulations. The free volume is calculated from the simulated cells of PVME by means of numerical methods based on grid scanning and probing the structure with a probe of a given radius R(P). The free-volume structure was found to be percolated for small probes at R(P)=0.