George Fytas

Max Planck Institute for Polymer Research

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Dimitris Vlassopoulos

FORTH Institute of Electronic Structure and Laser

Benoît Loppinet

Foundation for Research and Technology Hellas

Spiros H. Anastasiadis

Foundation for Research and Technology Hellas

Bartłomiej Graczykowski

Adam Mickiewicz University in Poznań

Hans‐Jürgen Butt

Max Planck Institute for Polymer Research

Yu Cang

Tongji University

Zuyuan Wang

University of Electronic Science and Technology of China

George Floudas

Max Planck Institute for Polymer Research

Krzysztof Matyjaszewski

Carnegie Mellon University

Nikos Hadjichristidis

King Abdullah University of Science and Technology

Cooperative Institutions

Max Planck Institute for Polymer Research

202

Foundation for Research and Technology Hellas

121

Max Planck Society

109

University of Crete

FORTH Institute of Electronic Structure and Laser

University of Applied Sciences Mainz

Johannes Gutenberg University Mainz

Eindhoven University of Technology

Centre National de la Recherche Scientifique

John Wiley & Sons (United States)

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ChemInform Abstract: A LIGHT SCATTERING STUDY OF THE MOLECULAR MOTION IN 1,2,6‐HEXANETRIOL

Chemischer Informationsdienst (1979)

T. Dorfmueller H. Dux George Fytas W. Mersch

10.1002/chin.197948082

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Non-Lorentzian Rayleigh spectra of bulk homopolymers far above the glass transition

Physical review. B, Condensed matter (1994)

F. Álvarez Juan Colmenero J. Kanetakis George Fytas

Non-Lorentzian depolarized Rayleigh-scattering spectra have been clearly observed by Fabry-Perot interferometry in bulk homopolymers, polyisoprene and 1,4-polybutadiene, far above the glass-transition temperature. We have developed two alternative phenomenological methods for analyzing this kind of spectra. First of all we have used a scattering model function based on the Havriliak-Negami relaxation function which, in fact, is compatible with a Kohlrausch-Williams-Watts relaxation function in the time domain. In the case of polyisoprene, the results obtained by this method are in good agreement with the obtained ones through other different relaxation techniques when a similar method of analysis is applied. Besides, we have extended to the frequency domain the contin algorithm which calculates an apparent distribution function of relaxation times from nonexponential time domain relaxation functions. The results obtained as well as the applicability of both methods are discussed.

10.1103/physrevb.49.14996

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Citations (16)

Structural Relaxation of Polymer Nanospheres under Soft and Hard Confinement: Isobaric versus Isochoric Conditions

ACS Nano (2011)

Yunlong Guo Chuan Zhang Christine Lai Rodney D. Priestley Maria D’Acunzi

We have measured the glassy-state structural relaxation of aqueous suspended polystyrene (PS) nanoparticles (the case of soft confinement) and the corresponding silica-capped PS nanoparticles (the case of hard confinement) via differential scanning calorimetry. Suspended and capped PS nanoparticles undergo physical aging under isobaric and isochoric conditions, respectively. With decreasing diameter, suspended and capped PS nanoparticles exhibited reduced and bulk glass transition temperatures (T(g)), respectively. To account for T(g) changes with confinement, all physical aging measurements were performed at a constant value of T(g) - T(a), where T(a) is the aging temperature. With decreasing diameter, aqueous suspended PS nanoparticles exhibited enhanced physical aging rates in comparison to bulk PS. Due to differences in thermodynamic conditions during aging and interfacial effects from nanoconfinement, at all values of T(g) - T(a) investigated, capped PS nanoparticles aged at reduced rates compared to the corresponding aqueous suspended PS nanoparticles. We captured the physical aging behavior of all nanoparticles via the Tool, Narayanaswamy, and Moynihan model of structural relaxation.

Isochoric process

Isobaric process

Polystyrene

10.1021/nn201751m

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Citations (61)

Study of viscoelastic relaxation in amorphous polypropylene near Tg by dynamic light scattering and shear creep

Macromolecules (1988)

George Fytas K. L. Ngai

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudy of viscoelastic relaxation in amorphous polypropylene near Tg by dynamic light scattering and shear creepG. Fytas and K. L. NgaiCite this: Macromolecules 1988, 21, 3, 804–811Publication Date (Print):March 1, 1988Publication History Published online1 May 2002Published inissue 1 March 1988https://doi.org/10.1021/ma00181a042RIGHTS & PERMISSIONSArticle Views270Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

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Polypropylene

10.1021/ma00181a042

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Citations (47)

Photon correlation spectroscopic measurement of the bulk compliance of poly(vinyl acetate) above T g

Journal of Applied Physics (1985)

Chen Wang J.-U. Hagenah G. Meier George Fytas E. W. Fischer

The technique of determining the longitudinal compliance over a wide dynamic range (from 10−1 to 106 Hz) using Rayleigh–Brillouin scattering has been studied. The method of computing the longitudinal compliance spectrum from the time correlation of density fluctuations of poly(vinyl acetate), as determined by the photon correlation spectroscopic technique, is illustrated.

Vinyl acetate

Brillouin zone

10.1063/1.335835

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Citations (2)

Relaxation behaviour in bulk PIMA and PIMA-PMMA copolymer near T g

Steinkopff eBooks (2007)

F. Álvarez Juan Colmenero C. H. Wang George Fytas

The relaxation processes in the glass-transition temperature range of bulk PIMA and PIMA-PMMA copolymer have been studied by means of Photon Correlation Spectroscopy (PCS) and dielectric spectroscopy (DR). The experimental results were treated in a conistent way employing an inverse Laplace transform analysis of the density C ϱ(t) and dipole moment ϕμ(t) autocorrelation functions. The latter was obtained from the ɛ″ (ω) data utilizing a recently developed algorithm. For bulk PIMA, C ϱ(t) clearly shows two distinct relaxation processes, whereas ϕμ(t) is dominated by the slower (α-) relaxation mode. The fast process in C ϱ(t) is probably related to the rotation of the rigid isobornyl group about the C-O bond.The copolymer displays a β-relaxation process and a slower α-relaxation dielectric process in agreement with the PCS results. The molecular origin of these processes is outlined.

10.1007/bfb0116447

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Dendrimer-Based Transient Supramolecular Networks

Journal of the American Chemical Society (2005)

Ron M. Versteegen D. J. M. van Beek Rint P. Sijbesma Dimitris Vlassopoulos George Fytas

Association of a 16-fold excess of a monodisperse telechelic oligo(THF) (Mw = 1270 g/mol) containing two end groups that selectively bind to the 32 binding sites of a fifth generation dendritic host (Mw = 18 511 g/mol and radius Rh = 2.4 nm) results in the formation of reversible and dynamic supramolecular complexes. The structure of these complexes in solution depends strongly on the concentration. At low concentration, the two end groups of one guest are proposed to complex to the same host, and flowerlike structures are formed with a radius of Rh = 3.7 nm. At higher concentrations, both end groups of one guest are complexed to different hosts, forming a bridge between them. This gives rise to the formation of larger associates, and eventually to a transient supramolecular network. Dynamic light scattering unequivocally showed that three distinct relaxation processes, associated with the proposed structures, are present in this system. In addition to the dynamics related to the flowerlike (fast) and the transient network structures (slow), an intermediate dynamic process is attributed to the cooperative motion of a few (∼6) connected flowerlike structures. Rheological data elucidate the nature of the intermittent network responsible for the slowest process. A monofunctional guest, not capable of forming a network structure, was used as a reference, and starlike supramolecular structures are formed at all concentrations, indeed.

Transient (computer programming)

10.1021/ja051775g

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Citations (45)

Depolarized light scattering studies of liquids: 1,5- and 2,4-pentanediol

The Journal of Chemical Physics (1981)

George Fytas Th. Dorfmüller

The temperature dependence of the shear viscosity of the isometric pair 1,5-pentanediol and 2,4-pentanediol exhibits some remarkable differences in the liquid phase. The purpose of this study is to rationalize these differences in terms of molecular structure of the two diols. In order to achieve this, we performed low frequency depolarized light scattering measurements and auxiliary viscosity measurements of the bulk liquids and their solutions over a wide temperature (230–350 K) and concentration range (0.2< χ <1). The integrated scattering intensity is shown to be mainly induced by H-bonded intermolecular structures and indicates marked structural differences between the two liquids obviously due to the capacity of 2,4-pentanediol to form bulky ring structures. The relaxation times obtained from the spectral linewidth measurements indicate that the local microviscosity to which molecular segments are subject during rotational motions is markedly smaller than the macroscopic shear viscosity especially at lower temperatures in 2,4-pentanediol, whereas this difference is negligible in 1,5-pentanediol. Even small concentrations of a solvent tend to reduce this effect drastically.

Microviscosity

Laser linewidth

10.1063/1.441987

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Citations (29)

Dynamic light scattering from bulk poly(n‐hexylmethacrylate) near and above the glass transition

Journal of Polymer Science Part B Polymer Physics (1992)

L. Giebel G. E. A. Meier George Fytas E. W. Fischer

Abstract Photon correlation spectra of polarized scattered light from poly( n ‐hexylmethacrylate) PHMA (M w = 1.6·10 5 , T g = −5°C) have been studied in the temperature range of −2–25°C. The experimental time correlation functions over the time range 10 −6 −10 2 s were represented by the Kohlrausch‐Williams‐Watts (KWW) function exp{−( t /τ) β } with a virtually temperature‐independent distribution parameter β = 0.27 ± 0.02. The observed relaxation functions were also analyzed in terms of a continuous distribution of retardation times L (τ) by means of a direct inverse Laplace transformation. The computed L (τ) distributions reveal a broad single peak structure in agreement with the results of the single KWW fit. The temperature dependence of τ is very similar to that of the shift factors obtained from measurements of the shear modulus and the stress relaxation modulus in the glass‐rubber region. Conversely, the values of τ compare well with those extracted from the experimental dielectric loss peaks consistently represented in the time domain by the KWW function. These findings suggest that the slow density fluctuations in bulk PHMA are associated with the primary glass‐rubber or α‐relaxation, which, however, displays an unusual low apparent Arrhenius activation energy and a rather low β value. PHMA exhibits significant dynamic light scattering with correlation times faster than 10 −6 s near T g . © 1992 John Wiley & Sons, Inc.

Shear modulus

Atmospheric temperature range

10.1002/polb.1992.090301114

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Citations (21)

CCDC 1535517: Experimental Crystal Structure Determination

The Cambridge Structural Database (2017)

Bastian Dumslaff Anna N. Reuss Manfred Wagner Xinliang Feng Akimitsu Narita

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/ccdc.csd.cc1njttt

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