Call for papers Special issue on "Properties of thin polymer films"

In recent years, there have been numerous reports of anomalous behavior of polymers in thin films. These observations, encompassing both structural and dynamical behavior, have attracted a great deal of interest. Measurements showing such anomalous behavior include density (irreversible and reversible changes after annealing below the bulk glass transition temperature), film stability and dewetting, glass transition temperature, diffusion coefficient and chain conformation and relaxation. The lack of a definitive M_w dependence in many of these studies means that it is not yet clear if the molecular size is a defining parameter in these observations. Alternatively, the surface to volume ratio may make such systems dependent on the (equally poorly understood) properties of polymer surfaces and interfaces. Despite a growing literature in this area, it is becoming increasingly obvious that a clear understanding of thin film properties has not yet been reached. In particular in glassy thin polymer films a possible cause for the anomalous behavior may originate from sample preparation. The widely used process of spin coating can potentially produce samples that are far from equilibrium. While most studies use thin films that have been annealed above the bulk glass transition, it is not clear if this represents sufficient annealing because the terminal relaxation times may be much larger than typical annealing times. One of the key questions is: Are these deviations from equilibrium important enough to cause any measurable effects? What are the consequences of film preparation and the resulting non-equilibrium conformations of the polymers on measurements of film stability, glass transition temperature, diffusion coefficient, etc.? Alternatively, if these non-equilibrium effects are not responsible for the anomalies observed in the structural and dynamical properties of thin polymer films, then other explanations must be considered. In the search for a unifying concept to explain all aspects simultaneously (i.e., density, film stability, glass transition temperature, ...) and in order to provide a forum for an open and possibly controversial discussion, The European Physical Journal E - Soft Matter invites regular articles and comments on this topic. In addition we invite submission of well-founded conjectures which may be published together with complementary views (solicited by the Editors). Papers to be considered for this special issue should be submitted by August 15, 2001 to the Editorial Office of the European Physical Journal E Véronique Condé, Editorial Office of The European Physical Journal E, Université Paris Sud, bâtiment 510, 91405 Orsay Cedex, France Tel.: 33 (0)1 69 15 59 76, Fax: 33 (0)1 69 15 59 75, e-mail: conde@edpsciences.org and marked clearly to the attention of either Günter Reiter (Editor) or James Forrest (Guest Editor). We look forward to receiving your submission.     

Zwitterion radicals and anion radicals from electron transfer and solvent condensation with the fingerprint developing agent ninhydrin.

Ninhydrin (the fingerprint developing agent) spontaneously dehydrates in liquid ammonia and in hexamethylphosphoramide (HMPA) to form indantrione, which has a sufficiently large solution electron affinity to extract an electron from the solvent (HMPA) to produce the indantrione anion radical. In liquid NH(3), the presence of trace amounts of amide ion causes the spontaneous formation of an anion radical condensation product, wherein the no. 2 carbon (originally a carbonyl carbon) becomes substituted with -NH(2) and -OH groups. In HMPA, the indantrione anion radical spontaneously forms condensation products with the HMPA to produce a variety of zwitterionic radicals, wherein the no. 2 carbon becomes directly attached to a nitrogen of the HMPA. The mechanisms for the formation of the zwitterionic paramagnetic condensation products are analogous to that observed in the reaction of ninhydrin with amino acids to yield Ruhemann's Purple, the contrast product in fingerprint development. The formation of anion and zwitterionic radical condensation products from ninhydrin and nitrogen-containing solvents may represent an example of a host of analogous polyketone-solvent reactions.     

On triazoles XLIII. Synthesis of 1,2,4‐triazolyl isoquinolinium zwitter ions

Type 8 isoquinolinium zwitter ions were synthesised by the reaction of type 1 diketones or type 2 pyrylium salts with different 5‐amino‐3‐Q‐1H‐1,2,4‐triazoles. Spectroscopic and X‐ray diffraction evidence was given for the zwitter ion structure of the products obtained. The position of the negative charge on the 1,2,4‐tiazolium ring was proved by comparison of the cmr and uv spectra of the products obtained with the three possible N‐benzyl derivatives 14–16 prepared for this purpose.     

The importance of charge-separation reactions in tandem mass spectrometry of doubly protonated angiotensin II formed by electrospray ionization: Experimental considerations and structural implications

The occurrence of charge-separation reactions in tandem mass spectrometry of doubly protonated angiotensin II is demonstrated by the use of mass-analyzed ion kinetic energy spectrometry (MIKES) and kinetic energy release distributions (KERDs). Linked scans at a constant B/E severely discriminate against product ions formed by charge-separation reactions. Although the products are significantly more abundant in MIKES experiments, instrumental discrimination still makes quantitation of relative product ion abundances highly inaccurate. The most probable KERs (T _{m. p.}) and the average KERs (T _ave.) of the reactions are determined from the KERDs, and these values are compared to the KERs determined from the peak widths at half-height (T _{0. 5}). The measurement of T _{0. 5} is a poor approximation to T _{m. p.} and T _ave.. The T _{m. p.} is used to calculate a most probable intercharge distance, which is compared to results from molecular dynamics calculations. The results provide evidence with regard to the mechanisms of fragmentation of multiply charged ions and the location of the charge site in relation to the decomposition reactions.     

Differentially Private Significance Tests for Regression Coefficients

Many data producers seek to provide users access to confidential data without unduly compromising data subjects’ privacy and confidentiality. One general strategy is to require users to do analyses without seeing the confidential data; for example, analysts only get access to synthetic data or query systems that provide disclosure-protected outputs of statistical models. With synthetic data or redacted outputs, the analyst never really knows how much to trust the resulting findings. In particular, if the user did the same analysis on the confidential data, would regression coefficients of interest be statistically significant or not? We present algorithms for assessing this question that satisfy differential privacy. We describe conditions under which the algorithms should give accurate answers about statistical significance. We illustrate the properties of the proposed methods using artificial and genuine data. Supplementary materials for this article are available online.     

Size Matters: From Two-Dimensional AuI–TlI Metallopolymers to Molecular Complexes by Simple Variation of the Steric Demand

Bis(acetylido) aurates(I) and thallium(I) trifluoromethylsulfonates were used to synthesize Au^I–Tl^I metallopolymers, displaying novel and unusual structural motifs of the metal–metal backbones in the solid state: a discrete molecular cluster, 1D chains of interconnected dimers, tetramers, or dodecamers of Au–Tl units, and a 2D-plane network, consisting of alternating edge-linked (AuTl)₆ and (AuTl)₄ cycles. The formation of the different architectures was primarily controlled by the steric demand of the acetylide-substituent groups. Thus, the bulkiest 2,6-diisopropylphenyl derivative yielded a molecular cluster [Tl₂Au₃]. Most compounds showed bright visible photoluminescence with quantum yields of up to 25 % at ambient temperature. The color of the emitted light significantly differs with the network structure. Furthermore, theoretical studies of singlet excitations in the molecular cluster, as well as NMR and mass-spectrometric investigations of the fragmentation of the metallopolymers in solution are described in detail.     

Thermodynamic features of perfectly crystalline poly(3‐hexylthiophene) based on Flory's relation

Poly(3‐hexylthiophene) (P3HT) as a conjugated polymer has many electrical and photovoltaic applications. However, reliable values for the equilibrium melting temperature ( ${T°}_m$) and for the enthalpy of fusion of a perfect P3HT crystal ( ${\Delta H°}_m$) are still in doubt. In the published works, ${\Delta H°}_m$ ranges from 33 to 99 J/g. Here, the melting point of P3HT in P3HT‐diluent mixtures is measured with changing the diluent concentration. By satisfying the requirements of Flory relation, “working with the same polymer crystals” and “working in the equilibrium state,” usually neglected in the literature, a reliable value of ${\Delta H°}_m$ = 83 ± 2 J/g is obtained. The reported values for ${T°}_m$ of P3HT are also in a wide range, 260?300 °C. In this work, accurate applying of the Hoffman‐Weeks relation, against the effects of lamellar thickening, yields ${T°}_m$ = 272 ± 2 °C rather than 300 ± 2°C reported in the literature. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 431–437     

Determination of tocopherols and sterols in vegetable oils by solid-phase extraction and subsequent capillary gas chromatographic analysis.

In general, analyses of tocopherols and sterols are performed separately in vegetable oils. By applying solid-phase extraction (SPE) prior to capillary gas chromatography, a simple and reliable procedure for the quantification of both tocopherols and sterols in a single analytical run has been developed. SPE was used as sample clean up procedure for the separation of these minor components from the triacylglycerol matrix, replacing time consuming saponification or on-line LC-GC. The analysis of tocopherols and free sterols in five different vegetable oils illustrates robustness and reliability of this method outlined. Quantification of the analytes was performed by external calibration with reference substances and internal standardization. The recovery of the procedure as well as the repeatability of the quantitative results have been evaluated.