arXiv subjects

Aleksandra Drozd-Rzoska

Publications and source records attributed to Aleksandra Drozd-Rzoska.

22 records · Page 2Linked to original sources

arXiv2018

Universal behavior of the apparent fragility and the structural relaxation time for the high pressure previtreous effect

This report shows the universal previtreous behavior of the pressure related apparent fragility, i.e. the steepness index Basing on this finding, the 3-parameter relation for portraying the previtreous behavior of the primary (structural) relaxation time is derived. The fair portrayal of experimental data was shown for glass forming 8*OCB (liquid crystal), EPON 828 (resin) and diisobutyl phthalate, propylene carbonate (low molecular weight liquids). On decompressing, the dynamic crossover dynamic domains is clearly detected. All these recalls the mode-coupling-theory behavior, but for the pressure path. It is notable, the discussed description offers the fair portrayal of experimental data even in the extreme pressure range P up to 2.2 GPa.

cond-mat.soft↗

arXiv2018

Universal behavior of the apparent fragility in ultraslow glass forming systems

Despite decades of studies on the grand problem of the glass transition the question of well-defined universal patterns, including the key problem of the previtreous behavior of the primary (structural) relaxation time, remains elusive. This report shows the universal previtreous behavior of the apparent fragility, i.e. the steepness index . It is evidenced that , for and . Basing on this finding, the new 3-parameter dependence for portraying the previtreous behavior of the primary relaxation time has been derived: . The universality of obtained relations is evidenced for glass formers belonging to low molecular weight liquids, polymers (melt and solid), plastic crystals, liquid crystals, resins and relaxors. They exhibit clear preferences either for the VFT or for the critical-like descriptions, if recalled already used modeling. The novel relation can obey even above the dynamic crossover temperature, with the power exponent ranging between ~17 (liquid crystals) to ~ 57 (glycerol), what may indicate the impact of symmetry on the previtreous effect. Finally, the emerging similarity to the behavior in the isotropic phase of nematic liquid crystals is recalled.

cond-mat.soft↗

arXiv2018

Unique dynamic crossover in supercooled x,3-dihydroxypropyl acrylate (x = 1, 2) isomers mixture

The previtreous dynamics in glass forming monomer, glycerol monoacrylate (GMA), using broadband dielectric spectroscopy (BDS) was tested. Measurements revealed the clear dynamic crossover at temperature $T_B = 254$ K and the time scale $τ(T_B) = 5.4$ ns for the primary (structural) relaxation time and no hallmarks for the crossover for the DC electric conductivity $σ_{DC}$. This result was revealed via the derivative-based and distortions-sensitive analysis $dln{H_{a}}/d(1/T)$ vs. $1/T$, where $H_a$ is for the apparent activation energy. Subsequent tests of the fractional Debye-Stokes-Einsten relation $σ_{DC}(τ_α)^S = const$ showed that the crossover is associated with $S = 1$ (for $T>T_B$)->$S = 0.84$ (for $T<T_B$). The crossover is associated with the emergence of the secondary beta relaxation which smoothly develops deeply into the solid amorphous phase below the glass temperature $T_g$.

cond-mat.soft↗

arXiv2014

Anomalous decoupling dynamics in glycerol and its nanocolloid with silver nanoparticles

Orientational and translational decouplings in ultraviscous glass forming glycerol and its nanocolloid based on Ag nanoparticles, as the function of temperature and pressure up to challenging P more than 1.5 GPa, are discussed. The analysis is focused on the fractional Debye-Stokes-Einstein relation FDSE sigma times tau to the power S equals const., where tau and sigma are for the structural relaxation time and electric conductivity are functions of T and P, respectively. For temperature tests in glycerol the clear evidence for the almost coupled exponent S equals 1 was obtained. For the supercooled nanocolloid the crossover to the decoupled domain associated with S equals 0.91 was noted. In super pressed glycerol and the nanocolloid the clear cross over from the domain described by the exponent S equals 1 to S less than 1 appeared on the GPa domain. For the nanocolloid it is associated with particularly strong decoupling, related to S equals 0.5, and occurs at well-defined pressure. This can suggest a possible fluid-fluid transition. Questions related to the validity of the Debye-Stokes tau equals approx. eta over T and Maxwell tau equals approx. eta relations, where eta is for viscosity, are also addressed. Results obtained do not support the recently suggested universality of the fractional exponent describing orientational and translational decoupling.

cond-mat.soft↗