The relative permittivity, loss, and breakdown strength are reported for a commercial sample of bisphenol Apolycarbonate (comm-BPA-PC) and a purified sample of the same polymer (rp-BPA-PC) as well as for two new polycarbonates having low molecular cross-sectional areas, namely a copolymer of tetraaryl polycarbonate and BPA-PC (TABPA-BPA-PC) and a triaryl polycarbonate homopolymer (TriBPA-PC). The glass transition temperatures of the new polymers are higher than the T g of BPA-PC (187 and 191 C vs. 148 C). Relative permittivity and loss measurements were carried out from 10 to 10 5 Hz over a wide temperature range, and results for the aand c-relaxation regions are discussed in detail. For the a-relaxation, the isochronal peak position, T a , scales approximately with T g . On the other hand, the peak temperature for the crelaxation is approximately constant, independent of T g . Also, in contrast to what is observed for a, c exhibits a strong increase in peak height as temperature/frequency increases and a significant difference is found between Arrhenius plots determined from isochronal and isothermal data analyses. Next, the c-relaxation region for comm-BPA-PC and associated activation parameters show strong history/purity effects. The activation parameters also depend on the method of data analysis. The results shed light on discrepancies that exist in the lit-erature for BPA-PC.

Audio frequency dielectric relaxation studies were carried out over the temperature range 120 to 390 K on nanoscale mesoporous silica coated with polystyrene and nanoscale γ alumina. Two features are observed, both of which are attributed to water. A relaxation is observed at about 150 K and 1000 Hz that is thermally activated. The activation enthalpy is relatively high and the pre-exponential appears to be unusually low and to depend upon the water concentration. A model is presented that accounts for the apparently anomalous behaviour. This relaxation is attributed to water molecules bound at surface hydroxyl groups. A feature is found in the vicinity of 250 K and 1000 Hz that is associated with conductivity that varies as ωn. This response is attributed to hopping conductivity in loosely bound surface water.

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The relative permittivity has been measured at audio frequencies and low temperatures for nanocomposites composed of poly(ether imide) (PEI) and BaTiO3 nanoparticles, the nanoparticles in a cavity and polycrystalline BaTiO3. The data at room temperature, for the real part of the relative permittivity versus nanoparticle content of the heat-treated nanocomposites, are found to follow a recently proposed modified Hanai equation. Also, a low-temperature relaxation region (in the vicinity of 20 K) is found in the heat-treated nanocomposites. This relaxation region is also observed in measurements on the nanoparticles packed in a cavity and for the polycrystalline BaTiO3 materials. A relaxation associated with water in the PEI is observed in the as-prepared nanocomposites. Finally, the breakdown strength of the heat-treated nanocomposites is found to decrease as the nanoparticle content increases. Microstructure-level simulations of electric field statistics were carried out and show that matrix field intensification cannot account for all of the variation of breakdown strength with nanoparticle concentration.

Synthetic organic pigments are widely used in modern and contemporary works of art. They have been examined by a variety of techniques including spectroscopic methods such as Fourier transform infrared spectroscopy, Raman, and X‐ray powder diffraction as well as chromatographic or mass spectrometric techniques such as pyrolysis‐gas chromatography/mass spectrometry and laser desorption ionization mass spectrometry (LDI–MS). Often, a combination of techniques has been used to examine these pigments. This paper describes use of Raman spectroscopy to create a database of colorants including two pigments not previously reported, PO1 and PO2. Then, using Raman spectroscopy in combination with LDI–MS, samples from modern works of art by artists including Mark Rothko, Barnett Newman, and José de Rivera were examined in order to identify the pigments present. One finding was that Rothko used a variety of red pigments over the course of his career including PR11 which has not been previously reported in artwork, and PO2 found with its positional isomer PR1. Knowledge of the colorants serves to inform conservators about display and treatment decisions. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.