Nanoscopic-Confinement Effects on Local Dynamics

Anastasiadis, Spiros H.; Karatasos, K.; Vlachos, G.; Manias, Evangelos; Giannelis, Emmanuel P.

doi:10.1103/physrevlett.84.915

Cited by 288 publications

(364 citation statements)

References 37 publications

(40 reference statements)

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“…In the frame of this interpretation the high temperature peak of the filled samples results from the glass transition of the immobilized polymer layer around the filler particles, which is more precisely a glass transition gradient near the filler surface due to attractive polymer-filler interaction [13] as described by several authors. It was shown that the mobility of chain units adjacent to the filler surface differs considerably from the bulk resulting in an individual glass transition temperature of the interphase [14][15][16]. Hereby, the influence of this interphase on the macroscopic properties of the sample increases with the amount of filler.…”

Section: Discussionmentioning

confidence: 96%

Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay

Fritzsche¹,

Das²,

Jurk³

et al. 2008

Express Polym. Lett.

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Abstract. In order to improve the physical properties of elastomers and to get more insight into the polymer dynamics close to filler interphases a carboxylated nitrile rubber (XNBR) was filled with up to 10 phr of layered silicate and investigated by dielectric and dynamic-mechanical analysis as well as by IR spectroscopy. Three relaxation processes have been detected beside the electrode polarization effect obtained in dielectric measurements. The relaxation process at low temperatures can be assigned to the β-process due to the rotational motion of side groups. Its temperature dependence follows an Arrhenius-like behaviour and there is no significant change in the shape of this process with the incorporation of filler. The glass transition at medium temperature shows a Vogel-Fulcher-dependence but seems to be independent of filler as well. At higher temperatures a new relaxation process was detected which is probably due to the formation of zinc-carboxyl-clusters. In dielectric and dynamic-mechanical measurements this process increases with increasing loading of organoclay and is shifted to higher temperature.

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Section: Discussionmentioning

confidence: 96%

Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay

Fritzsche¹,

Das²,

Jurk³

et al. 2008

Express Polym. Lett.

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“…Consequently, it is possible that the observed IP or MWS effect consists of two contributions, which differ in their relaxation rate. In addition, intercalation of polymer chains within the layers results in increased relaxation rate or lower glass transition temperature [12,19,20], since the isolated polymer molecules are not involved in cooperative molecular motions. The influence of all the above contributions is reflected in the broad and complex shape of the loss modulus (M″) curve with frequency ( Figure 6b).…”

Section: Resultsmentioning

confidence: 99%

Relaxation phenomena in rubber/layered silicate nanocomposites

Psarras

Gatos²,

Karahaliou³

et al. 2007

Express Polym. Lett.

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The impact of nanomaterials and/or nanostructured materials is well known and well appreciated [1][2][3][4], mostly due to their potential applications based on their thermo-mechanical performance, flame resistance, electrical properties etc. Polymer matrix nanocomposites can be prepared by dispersing a small amount of nanometer size filler within the host medium. Rubber/Layered Silicate (LS) nanocomposites are increasingly attracting scientific and technological attention, because of the high reinforcing efficiency of the LS, even at very low loading. Polymer matrix/LS nanocomposites exhibit three different configurations: (a) microphase separated composites, where polymer matrix and layered silicates remain immiscible, (b) intercalated structures, where polymer molecules are inserted between the silicate layers, and (c) exfoliated structures, where individual silicate layers are dispersed in the polymer matrix. Polymer matrix nanocomposites are expected to be useful in replacing conventional insulating materials providing tailored performance, by simply controlling the type and the concentration of nanoinclusions [5][6][7][8]. 'Nanodielectrics' is a rather new term associating dielectrics with nanotechnology [9]. Nanoinclusions could be able to serve as inherent nanocapacitors. Charging and discharging 837 * Corresponding author, e-mail: G.C.Psarras@upatras.gr © BME-PT and GTE Abstract. Broadband Dielectric Spectroscopy (BDS) is employed in order to investigate relaxation phenomena occurring in natural rubber (NR), polyurethane rubber (PUR) and PUR/NR blend based nanocomposites, reinforced by 10 parts per hundred (phr) Layered Silicates (LS). Nanocomposites and matrices were examined under identical conditions in a wide frequency (10 -1 to 10 6 Hz) and temperature (-100 to 50°C) range. Experimental data are analyzed in terms of electric modulus formalism. The recorded relaxation phenomena include contributions from both the polymer matrices and the nanofiller. Natural rubber is a non-polar material and its performance is only slightly affected by the presence of layered silicates. Polyurethane rubber exhibits four distinct relaxation processes attributed, with ascending relaxation rate, to Interfacial Polarization (IP), glass/rubber transition (α-mode), local motions of polar side groups and small segments of the polymer chain (β, γ-mode). The same processes have been detected in all systems containing PUR. IP is present in all nanocomposites being the slowest recorded process. Finally, pronounced interfacial relaxation phenomena, occurring in the PUR+10 phr LS spectra, are attributed to nanoscale effects of intercalation and exfoliation.Keywords : polymer composites, nanocomposites, dielectric spectroscopy, relaxations, rubber eXPRESS Polymer Letters Vol.1, No.12 (2007) [837][838][839][840][841][842][843][844][845] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2007.116 under control the embedded in a matrix nanocapacitors, defines an energy storing procedure at the nanoscal...

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“…Such a decrease has been alluded to in previous simulations of shorter chains in the continuum 12 and longer chains on a lattice, 13 and has been observed experimentally in intercalated polymer films. 23 A higher probability of low-frequency modes can have important implications for glassy dynamics; a greater number of directions with lower curvature could facilitate the escape from a basin and rationalize the observed depression of T g . Furthermore, in both the bulk and thin-film geometries, these modes correspond to motions that are correlated over larger length scales than other modes.…”

Section: Resultsmentioning

confidence: 99%

Influence of confinement on the vibrational density of states and the Boson peak in a polymer glass

Jain

Pablo

2004

The Journal of Chemical Physics

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We have performed a normal-mode analysis on a glass forming polymer system for bulk and free-standing film geometries prepared under identical conditions. It is found that for free-standing film glasses, the normal-mode spectrum exhibits significant differences from the bulk glass with the appearance of an additional low-frequency peak and a higher intensity at the Boson peak frequency. A detailed eigenvector analysis shows that the low-frequency peak corresponds to a shear-horizontal mode which is predicted by continuum theory. The peak at higher frequency ͑Boson peak͒ corresponds to motions that are correlated over a length scale of approximately twice the interaction site diameter. These observations shed some light on the microscopic dynamics of glass formers, and help explain decreasing fragility that arises with decreasing thickness in thin films.

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Nanoscopic-Confinement Effects on Local Dynamics

Cited by 288 publications

References 37 publications

Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay

Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay

Relaxation phenomena in rubber/layered silicate nanocomposites

Influence of confinement on the vibrational density of states and the Boson peak in a polymer glass

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