Glass-Forming Liquids in Mesopores Probed by Solvation Dynamic and Dielectric Techniques

Yan, X.; Streck, C.; Richert, Ranko

doi:10.1557/proc-464-33

Cited by 12 publications

(11 citation statements)

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“…16 For a polar filler such as D-sorbitol in a dielectrically inert matrix, a quantitative analysis requires determining f *(ω) on the basis of c *(ω) and m *(ω). 17 Being interested mainly in the confinement effects associated with the β-relaxation, we can refrain from such a calculation because f *(ω) ≈ m *(ω) in the glassy state of D-sorbitol. In this special case, the Maxwell-Wagner equation reduces practically to a linear rescaling which corrects for the volume fraction of the filler.…”

Section: Resultsmentioning

confidence: 99%

“…According to the Maxwell−Wagner−Sillars theory, the composite dielectric function ε c *( ω ) depends in a nonlinear fashion on the dielectric properties of the filler material, ε f *( ω ), and of the silica glass matrix having ε m *( ω ) ≈ 3, where φ is the filler volume fraction and n is the depolarization factor with n = 1/3 for spherical particles . For a polar filler such as d -sorbitol in a dielectrically inert matrix, a quantitative analysis requires determining ε f *( ω ) on the basis of ε c *( ω ) and ε m *( ω ) . Being interested mainly in the confinement effects associated with the β-relaxation, we can refrain from such a calculation because ε f *( ω ) ≈ ε m *( ω ) in the glassy state of d -sorbitol.…”

Section: Resultsmentioning

confidence: 99%

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Equilibrium and Non-Equilibrium Type β-Relaxations: d-Sorbitol versus o-Terphenyl

1999

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A previous observation, which indicated that the β-relaxation intensity of o-terphenyl is sensitive to the thermal history, is substantiated by dielectric relaxation experiments. Unlike the β-processes of other materials, only the quenched glassy state of o-terphenyl displays this secondary relaxation feature. The β-intensity is observed to decay gradually upon annealing and disappears altogether in the equilibrium liquid state at T > T g. We compare the case of o-terphenyl with the concomitant signatures of d-sorbitol, which represents the more typical case of a glass-former which exhibits the slow β-process also in the liquid state including the α−β-merging scenario. We also present data of this α−β-merging for d-sorbitol confined to pores of 5 nm diameter, indicating that no longer-ranged correlations are involved in the secondary process.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Equilibrium and Non-Equilibrium Type β-Relaxations: d-Sorbitol versus o-Terphenyl

1999

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“…Because the progress of the relaxation is monitored in terms of a time dependent redshift of the emission energy of solute molecules, the amount of volume probed and the signal intensities do not affect the results directly. Furthermore, ambiguities resulting from dielectric mixing effects [25][26][27] remain absent in these experiments. In recent studies, we have used triplet state solvation techniques for focusing on the dynamics of a confined liquid at the liquid/solid interface, 28 and for comparing hard versus soft boundary conditions.…”

Section: Introductionmentioning

confidence: 95%

Dynamics of supercooled liquids in the vicinity of soft and hard interfaces

He¹,

Wang²,

Richert³

2005

Phys. Rev. B

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Using solvation techniques we explore the dynamics of nanoconfined and interfacial supercooled liquids near their glass transition temperatures. Confinement is accomplished by the use of porous glasses with pore diameters between 4 and 7.5 nm, and by microemulsions with droplet sizes between 2.6 and 5 nm. Via the attachment of the probe molecules to the inner surface of porous glasses filled with 3-methylpentane, the interfacial layer is measured selectively for different surface curvatures and shows an increase of the relaxation time by more than three orders of magnitude over that of the bulk liquid. This frustration is most pronounced at the pore boundary and decreases gradually across the first few nanometers distance away from the interface. Nanoconfinement realized by glass-forming microemulsions with the confining material being more fluid than the intramicellar droplets reverse the situation from frustrated dynamics in hard confinement to accelerated relaxation behavior in the case of soft boundaries. Without changing the size of the geometrical restriction of propylene glycol, hard versus soft boundary conditions changes the glass transition shift ⌬T g from +6 K to − 7 K. The findings can be rationalized on the basis of certain interfacial dynamics which differ from bulk behavior, with the penetration of this effect into the liquid being governed by the length scale of cooperativity. This picture explains both the more disperse relaxation times in confinement and the dependence of the average relaxation time on pore size.

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“…glass transition | thin film | interfacial dynamics | elastic activation | nanoconfinement S patially heterogeneous dynamics in glass-forming liquids confined to nanoscale domains (1-7) play a major role in determining the properties of molecular, polymeric, colloidal, and other glass-forming materials (8), including thin films of polymers (9,10) and small molecules (11)(12)(13)(14)(15), small-molecule liquids in porous media (2,4,16,17), semicrystalline polymers (18,19), polymer nanocomposites (20)(21)(22), ionomers (23)(24)(25), self-assembled block and layered (26)(27)(28)(29)(30)(31)(32)(33) copolymers, and vapor-deposited ultrastable molecular glasses (34)(35)(36). Intense interest in this problem over the last 30 y has also been motivated by the expectation that its understanding could reveal key insights concerning the mechanism of the bulk glass transition.…”

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confidence: 99%

Nature of dynamic gradients, glass formation, and collective effects in ultrathin freestanding films

Ghanekarade

Phan

Schweizer

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Molecular, polymeric, colloidal, and other classes of liquids can exhibit very large, spatially heterogeneous alterations of their dynamics and glass transition temperature when confined to nanoscale domains. Considerable progress has been made in understanding the related problem of near-interface relaxation and diffusion in thick films. However, the origin of “nanoconfinement effects” on the glassy dynamics of thin films, where gradients from different interfaces interact and genuine collective finite size effects may emerge, remains a longstanding open question. Here, we combine molecular dynamics simulations, probing 5 decades of relaxation, and the Elastically Cooperative Nonlinear Langevin Equation (ECNLE) theory, addressing 14 decades in timescale, to establish a microscopic and mechanistic understanding of the key features of altered dynamics in freestanding films spanning the full range from ultrathin to thick films. Simulations and theory are in qualitative and near-quantitative agreement without use of any adjustable parameters. For films of intermediate thickness, the dynamical behavior is well predicted to leading order using a simple linear superposition of thick-film exponential barrier gradients, including a remarkable suppression and flattening of various dynamical gradients in thin films. However, in sufficiently thin films the superposition approximation breaks down due to the emergence of genuine finite size confinement effects. ECNLE theory extended to treat thin films captures the phenomenology found in simulation, without invocation of any critical-like phenomena, on the basis of interface-nucleated gradients of local caging constraints, combined with interfacial and finite size-induced alterations of the collective elastic component of the structural relaxation process.

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Glass-Forming Liquids in Mesopores Probed by Solvation Dynamic and Dielectric Techniques

Cited by 12 publications

References 13 publications

Equilibrium and Non-Equilibrium Type β-Relaxations: d-Sorbitol versus o-Terphenyl

Equilibrium and Non-Equilibrium Type β-Relaxations: d-Sorbitol versus o-Terphenyl

Dynamics of supercooled liquids in the vicinity of soft and hard interfaces

Nature of dynamic gradients, glass formation, and collective effects in ultrathin freestanding films

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