Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering

Patkowski, A.; Thurn‐Albrecht, Thomas; Banachowicz, Ewa; Steffen, Werner; Bösecke, P.; Narayanan, Theyencheri; Fischer, Erhard W.

doi:10.1103/physreve.61.6909

Cited by 51 publications

(46 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…While all techniques [NMR (7,8,11), dielectric hole-burning (13,16), light scattering (19), x-ray scattering (18), and fluorescence (6)] agree on the presence of dynamical heterogeneity, no such consensus exists about environmental exchanges. For example, exchange times are on the order of the alpha-relaxation times according to NMR (7) and dielectric relaxation (16) measurements, whereas optical techniques rather point to very slow exchange and relaxation processes (6,9,10,15,(18)(19)(20)(21). To clarify this apparent contradiction, we note that the properties of a heterogeneous ensemble of molecules in a glass-forming liquid will be spread along many dimensions.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, spatially inhomogeneous dynamics (5) have been observed with a variety of techniques in many glass formers, including simple liquids (6-10) and polymers (11)(12)(13)(14)(15). Inhomogeneities have been found in the particular case of supercooled glycerol by dielectric hole burning (16), NMR (17), x-ray (18), light scattering (19), and stimulated Brillouin gain spectroscopy experiments (20,21). These observations have to be reconciled with the common view of a supercooled liquid, which is supposed to remain a normal ergodic liquid until the glass transition.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules

Zondervan

Kulzer

Berkhout

et al. 2007

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

147

180

View full text Add to dashboard Cite

We probe the rotational diffusion of a perylene dye in supercooled glycerol, 5-25 K above the glass-transition temperature (T g ‫؍‬ 190 K) at the ensemble and the single-molecule level. The singlemolecule results point to a broad distribution of local viscosities that vary by a factor of five or more for different individual fluorophores at a given temperature. By following the same single molecules at various temperatures, we find that the distribution of local viscosities itself broadens upon approaching T g. This spatial heterogeneity is found to relax extremely slowly, persisting over hours or even days. These results convey a picture of heterogeneous liquid pockets separated by solid-like walls, which exist already well above the viscosimetric glass transition.fluorescence ͉ glass transition ͉ anisotropy ͉ correlation G lycerol is an archetypal molecular glass former. Although glycerol crystals can be grown from solution, the pure liquid readily supercools because of its high viscosity [10 3 times that of water at room temperature (1)], which is caused by the formation of a highly branched network of intermolecular hydrogen bonds. The viscosity of supercooled glycerol increases by 10 orders of magnitude between 291.8 K, the melting temperature of crystalline glycerol, and its viscosimetric glass-transition temperature T g ϭ 190 K. Throughout this range of temperatures, macroscopic rheology measurements seem consistent with the expected behavior of a Newtonian liquid, although they also reveal highly nonexponential kinetics (1-3).The necessity for cooperative motion at larger and larger scales on approaching the glass transition was recognized a long time ago by Adam and Gibbs (4). In their view, glass formation arises from dynamical arrest of cooperative domains, and their spread in sizes leads to an overall nonexponential relaxation. Indeed, spatially inhomogeneous dynamics (5) have been observed with a variety of techniques in many glass formers, including simple liquids (6-10) and polymers (11-15). Inhomogeneities have been found in the particular case of supercooled glycerol by dielectric hole burning (16), NMR (17), x-ray (18), light scattering (19), and stimulated Brillouin gain spectroscopy experiments (20, 21). These observations have to be reconciled with the common view of a supercooled liquid, which is supposed to remain a normal ergodic liquid until the glass transition. Heterogeneous regions with different relaxation dynamics are therefore expected to exchange with one another to restore ergodicity, by processes called environmental exchanges (6,9,10,12,(14)(15)(16). The typical mechanisms, length scales, and time scales of environmental exchanges remain largely unclear. NMR and dielectric relaxation point to times comparable to the molecular rotation times (16,22), whereas light scattering and fluorescence show inhomogeneities with exceedingly slow relaxation (9,12,(19)(20)(21).Single-molecule fluorescence is a well established method for studying rotational diffusion (23-26). Linear dichroism...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules

Zondervan

Kulzer

Berkhout

et al. 2007

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

147

180

View full text Add to dashboard Cite

show abstract

“…The approach of the glass transition is thought to lead to spatial heterogeneity on increasing length scales and the formation of mesoscopic structure sometimes referred to as Fischer clusters. [27,28] Such behavior can be explained by a locally favored structure that is not the structure corresponding to the global enthalpy minimum. [29,30] For example, in a Lennard-Jones liquid, the locally favored structure is an icosahedron whereas the global minimum enthalpy is achieved for an fcc or hcp lattice.…”

Section: Introductionmentioning

confidence: 99%

Rattling the cage: Micro- to mesoscopic structure in liquids as simple as argon and as complicated as water

Turton

Hunger

Stoppa

et al. 2011

Journal of Molecular Liquids

View full text Add to dashboard Cite

ÔØ Å ÒÙ× Ö ÔØThis is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract. The water molecule has the convenient property that its molecular polarizability tensor is nearly isotropic while its dipole moment is large. As a result, the low-frequency anisotropic Raman spectrum of liquid water is mostly collision induced and therefore reports primarily translational motions while the far-infrared (terahertz) and dielectric spectrum is dominated by rotational modes. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTAtomic and globular-molecular liquids have a zero dipole moment as well as an isotropic polarizability tensor. These spectrum-simplifying properties were exploited in a study of a number of liquids and solutions using ultrafast optical Kerr-effect (OKE) spectroscopy combined with dielectric relaxation spectroscopy (DRS), terahertz time-domain spectroscopy (THz-TDS), and terahertz field-induced second-harmonic generation (TFISH) spectroscopy. For room-temperature ionic liquids (RTILs), liquid water, aqueous salt solutions, noble gas liquids, and globular molecular liquids it was found that, in each case, surprising structure and/or inhomogeneity is observed, ranging from mesoscopic clustering in RTILs to stretched exponential dynamics in the noble gas liquids. For aqueous electrolyte solutions it is shown that the viscosity, normally described by the Jones-Dole expression, can be explained in terms of a jamming transition, a concept borrowed from soft condensed matter studies of glass transitions in colloidal suspensions.

show abstract

“…Heterogeneity is readily observed in optical experiments on supercooled liquids, notably in light and x-ray scattering (3,4), polarized hole-burning (5,6), and single-molecule spectroscopy (7,8), and it appears to relax slowly. Tracking of individual particles in colloidal glasses (9,10), as well as computer simulations (11)(12)(13), provides further evidence for heterogeneity and confirms that relaxation is driven by collective rearrangements.…”

mentioning

confidence: 99%

Soft glassy rheology of supercooled molecular liquids

Zondervan

Xia

Meer

et al. 2008

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

View full text Add to dashboard Cite

We probe the mechanical response of two supercooled liquids, glycerol and ortho-terphenyl, by conducting rheological experiments at very weak stresses. We find a complex fluid behavior suggesting the gradual emergence of an extended, delicate solidlike network in both materials in the supercooled state-i.e., above the glass transition. This network stiffens as it ages, and very early in this process it already extends over macroscopic distances, conferring all well known features of soft glassy rheology (yieldstress, shear thinning, aging) to the supercooled liquids. Such viscoelastic behavior of supercooled molecular glass formers is difficult to observe because the large stresses in conventional rheology can easily shear-melt the solid-like structure. glass transition ͉ glycerol ͉ ortho-terphenyl ͉ yield-stress

show abstract

Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering

Cited by 51 publications

References 23 publications

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules

Rattling the cage: Micro- to mesoscopic structure in liquids as simple as argon and as complicated as water

Soft glassy rheology of supercooled molecular liquids

Contact Info

Product

Resources

About

Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering

Cited by 51 publications

References 23 publications

Local viscosity of supercooled glycerol near T g probed by rotational diffusion of ensembles and single dye molecules

Local viscosity of supercooled glycerol near T g probed by rotational diffusion of ensembles and single dye molecules

Rattling the cage: Micro- to mesoscopic structure in liquids as simple as argon and as complicated as water

Soft glassy rheology of supercooled molecular liquids

Contact Info

Product

Resources

About

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules

Local viscosity of supercooled glycerol near T _g probed by rotational diffusion of ensembles and single dye molecules