Temperature dependence of the electrical conductivity of imidazolium ionic liquids.

The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393 K on the basis of dielectric measurements in the frequency range from 1 to 10^7 Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion.ionic liquids; molten salts;

Guanidinium nonaflate as a solid-state proton conductor

Guanidinium nonaflate, a novel pure protic organic ionic plastic crystal (POIPC) with an elegant symmetrical cation, is discovered to be a new solid-state proton conductor.</p

Book review: Broadband Dielectric Spectroscopy, ed. by by Friedrich Kremer and Andreas Schonhals

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Glass transition effects in ultra-thin polymer films

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Sensoren auf der Basis von Polymeren

The detection of a strong piezoelectric effect in the fluoropolymer polyvinylidene fluoride (PVDF) was the beginning of the development of sensors and transducer technology. The structure of PVDF, which is derived from polymerization of CF6=CH2, and the production of films are described. The general relationships between the electrical field, the dielectric shift, the mechanical stress and the elastic deformation are derived. The measurement of the piezoelectric properties of very thin polymer foils is carried out using the Rezvani/Linvill method. The measuring equipment is schematically illustrated. Piezoelectric PVDF foils are used in supersonic transducers, microphones, hydrophones, power, pressure and acceleration equipment.status: publishe

Asymmetric polarization and hysteresis behaviour in ferroelectric P(VDF-TrFE) (76:24) copolymer thin films spatially resolved via LIMM

The concept of charge polarization coupling in the ferroelectric copolymer PVDF TrFE(poly[(vinylidene fluoride co trifluoroethylene]) has been revisited by employing high resolution (<50 nm) pyroelectric depth profiling (LIMM). By virtue of probing the pyroelectric activity over the film thickness in the presence of a variable, external electrical field, the local ferroelectric response and spatially resolved hysteresis could be obtained. A large asymmetry was found between the positive and negative electrode polymer interface. Differences in amplitude of polarization, contribution of interface charges and length scale of the polarization free zone near the electrodes suggest a higher availability of compensation charges at the negative electrode that finally stabilize the local polarization. The resulting asymmetries in the polarization distribution are hence attributed to excess charges as a result of electron injection as a specific charge generation mechanism at the negative electrode.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The PCCP Owner Societies have an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 23 December 2014; Accepted 17 February 2015; Accepted Manuscript published 17 February 2015; Advance Article published 25 February 2015; Version of Record published 11 March 2015status: publishe

Deviation from bulk behaviour in the cold crystallization kinetics of ultrathin films of poly(3-hydroxybutyrate)

The cold crystallization kinetics of ultrathin films of poly( 3-hydroxybutyrate) ( PHB) have been investigated by dielectric spectroscopy. Upon reduction of the film thickness, a lowering of the Avrami exponent accompanied by an increase of the crystallization time was observed. The experimental results are analysed in terms of reduction of the total number of nuclei involved in the crystallization process.status: publishe

Deviations from Bulk Glass Transition Dynamics of Small Molecule Glass Formers: Some Scenarios in Relation to the Dimensionality of the Confining Geometry

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Monitoring the cold crystallization of poly(3-hydroxy butyrate) via dielectric spectroscopy

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