Most glass-forming systems are composed of basic units interacting with each other a nontrivial anharmonic potential. Naturally, relaxation and diffusion in glass formers is many-body problem. Results from recent experimental studies presented to show the effects manifested on dynamic properties formers. Considering that general critical, problem transition will not be solved until nature process has been incorporated fundamentally into any theory.

We report evidence from broadband dielectric spectroscopy that the dynamics of primary alpha- and secondary Johari-Goldstein (JG) beta-processes are strongly correlated in different glass-forming systems over a wide temperature T pressure P range, contrast with widespread opinion statistical independence these processes. The alpha-beta mutual dependence is quantitatively confirmed by (a) overall superposition spectra measured at T-P combinations but an invariant alpha-relaxation time; (b)...

By now it is well established that the structural α-relaxation time, τα, of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τα a function Φ product variable, ργ/T, where ρ density T temperature. The constant γ as function, = Φ(ργ/T), material dependent. Actually this dependence on ργ/T originates from same variable Johari-Goldstein β-relaxation τβ, or primitive relaxation τ0, coupling model. To support assertion, we give evidences...

The structural dynamics of ultrathin polymer films poly(ethylene terephthalate) capped between aluminum electrodes have been investigated by dielectric relaxation spectroscopy. A deviation from bulk behavior, appearing as an increase the time at a fixed temperature, is observed for thickness below 35 nm. slowing down acts constant shift factor independent and fragility constant. interfacial energy calculated to be 3 mJ/m2, confirming strong interaction substrate, which leads presence layer...

Zhu et al. [L. Zhu, C. W. Brian, S. F. Swallen, P. T. Straus, M. D. Ediger, and L. Yu, Phys. Rev. Lett. 106, 256103 (2011)] measured the surface self-diffusion for an organic glass former, indomethacin, found diffusion is more than 10${}^{6}$ times faster bulk at temperatures around ${T}_{g}$. With help of dielectric relaxation differential scanning calorimetry measurements on analysis data using coupling model, we provide a quantitative explanation. We find \ensuremath{\alpha}-relaxation...

The paper (Sibik, J.; Elliott, S. R.; Zeitler, J. A. Phys. Chem. Lett. 2014, 5, 1968–1972) used terahertz time-domain spectroscopy (THz-TDS) to study the dynamics of polyalcohols, glycerol, threitol, xylitol, and sorbitol, at temperatures from below above glass transition temperature Tg. On heating glasses, they observed dielectric losses, ε″(ν) ν = 1 THz, increase monotonically with change dependence two temperatures, first deep in glassy state TTHz 0.65Tg second effects both are most...

Dielectric relaxation measurements of a typical small molecular glassformer, dipropyleneglycol dibenzoate show the presence two secondary relaxations. Their dynamic properties differ in equilibrium liquid and glassy states, as well changes during structural recovery after rapid quenching to form glass. These differences enable us identify slower genuine Johari-Goldstein (JG) beta-relaxation, acting precursor primary alpha-relaxation. Agreement between JG beta-relaxation time independent...

The effects of supporting substrate and thermal annealing on plasticization poly(vinyl acetate) ultrathin films by absorption ambient moisture have been studied local dielectric spectroscopy. Upon exposure to moisture, the relaxation rate α-process increases a different extent at variance film thicknesses substrates. Namely, hydrophobic gold substrates speeding up is slightly reduced decrease thickness down about 20 nm. Moreover, increase measured 21 nm thick supported smaller compared that...

The influence of interfacial interactions and annealing time on dynamics the α-relaxation in ultrathin poly(vinyl acetate) films deposited different substrates has been studied using local dielectric spectroscopy at ambient pressure controlled humidity. After 323 K for about 3 days, polymer supported gold aluminum substrates, an increase relaxation rate with decreasing film thickness below 30–35 nm was observed, whereas silicon a thickness-independent found as thin 12 nm. difference size...

At temperatures below the nominal glass transition temperature Tgα, structural α-relaxation and Johari-Goldstein (JG) β-relaxation are too slow to contribute susceptibility measured at frequencies higher than 1 GHz. This is particularly clear in neighborhood of secondary Tgβ, which can be obtained directly by positronium annihilation lifetime spectroscopy (PALS) adiabatic calorimetry, or deduced from JG time τβ reaches 1000 s. The fast process such high comes vibrations caged molecules...

In the first two papers separately on polyalcohols and amorphous polymers of this series, we demonstrated that fast dynamics observed in glassy state at high frequencies above circa 1 GHz is caged dynamics. We showed generally intensity changes temperature dependence a THF nearly coincident with secondary glass transition Tgβ lower than nominal Tgα. The phenomenon remarkable, since determined from measurements short time scales typically ns to ps range, while characterizes which...

The effect of severe confinement on the dynamics three different generations hyperbranched polyesters Boltorn family is investigated by dielectric relaxation spectroscopy (DRS). polymer chains are intercalated within galleries natural montmorillonite (Na+-MMT), thus forming 1 nm films confined between solid walls. structure nanocomposites studied with X-ray diffraction and thermal behavior polymers in bulk under determined differential scanning calorimetry. glass transition temperatures show...

In semi‐crystalline polymers, amorphous segments located in different regions and distance from the crystalline domains can exhibit dynamics. poly( l ‐lactic acid) (PLLA), existence of (i) two distinct mobile fractions (a completely fraction a slightly constrained fraction), which vitrify/devitrify T g region, (ii) rigid fraction, vitrifies/devitrifies at temperatures higher than , has been reported literature. The percentage three fractions, characterized by segmental mobility, is generally...

Abstract The nanobubble inflation method is the only experimental technique that can measure viscoelastic creep compliance of unsupported ultrathin films polymers over glass–rubber transition zone as well dependence glass temperature ( T g ) on film thickness. Sizeable reduction was observed in polystyrene (PS) and bisphenol A polycarbonate by shift to shorter times. thickness consistent with published data free‐standing PS films. However, accompanying times, a decrease rubbery plateau...

Interfacial and confinement effects on the evolution of cooperativity approaching glass transition have been studied in poly(propylenecoethylene) functionalized with diethylmaleate, polyethylene 1,4-cyclohexylenedimethylene terephthalate glycol their nanocomposites montmorillonite. A small increase structural dynamic cooperativity, a weak alteration temperature dependence characteristic relaxation frequency, no changes observed poly(propylenecoethylene)-based samples can be rationalized...

Recent studies relate the slowing down of structural relaxation time supercooled liquids to a decrease excess entropy ${S}_{\mathrm{exc}}$ melt with respect crystal. The theoretical basis such result was often found in Adam Gibbs (AG) theory, implicitly assuming proportionality between and configurational ${S}_{c}$ system. This work presents direct test connection dynamics over wide temperature pressure interval for three different glass forming systems, o-terphenyl, triphenylchloromethane,...

Broadband dielectric measurements were carried out at isobaric and isothermal conditions up to 1.75 GPa for reconsidering the relaxation dynamics of decahydroisoquinoline, previously investigated by Richert et al. [R. Richert, K. Duvvuri, L.-T. Duong, J. Chem. Phys. 118, 1828 (2003)] atmospheric pressure. The time intense secondary tau(beta) seems be insensitive applied pressure, contrary alpha-relaxation times tau(alpha). Moreover, separation alpha- beta-relaxation lacks correlation between...

Local dielectric spectroscopy is performed to study how relaxation dynamics of a poly-vinyl-acetate ultra-thin film influenced by inorganic nano-inclusions layered silicate (montmorillonite). Dielectric loss spectra are measured electrostatic force microscopy in the frequency-modulation mode ambient air. Spectral changes both shape and time evidenced across boundary between pure polymer montmorillonite sheets. imaging also performed, evidencing spatial variations properties near...

The effect of confinement on structural relaxation in ultrathin poly(vinyl acetate) films has been studied by local dielectric spectroscopy. This scanning probe method allows the investigation at nanometer scale supported having a free surface. Measurements have performed ambient pressure and controlled atmosphere with decreasing thickness. A deviation dynamic properties from bulk behavior, showing up as an increase rate, was observed starting film thickness 35 nm, which corresponds to about...

The effect of isobaric cooling (over the range 190–350 K) and isothermal compression (up to 700 MPa) on structural α- secondary β-relaxations has been studied for low molecular weight glass-forming systems. shape α-loss peak was found change with temperature T pressure P but be constant a combination giving same τα(T,P). invariance at τα(T,P) involved also excess wing, i.e. process showing up high-frequency tail in systems no well-resolved β-process. Likewise, where wing evolved β-peak...

The Johari-Goldstein (JG) β-relaxation is supposedly a universal feature of glassy dynamics and has strong connections to structural α-relaxation in all glass-formers. On the other hand, some small molecular glass-formers give no indication that JG relaxation present, despite numerous investigations using variety experimental techniques. These exceptions cast doubt on universality fundamental importance. Theoretical considerations suggest present but unresolved these because it sandwiched...