Polymer blends - current state of progress and future developments from an industrial viewpoint

Technical and economic considerations have given polymer blends a major share in the increasing sales of plastics. This applies both to general-purpose and to the higher value-added materials. Thus it is scarcely surprising that almost all polymer manufacturers have now developed comprehensive ranges of blends having particular property profiles. The principal types of blends currently available are described. The variety of products already developed should not be allowed to obscure the fact that certain conceivable and highly attractive property combinations have not so far been realized. If progress is to be made in this area, interdisciplinary cooperation between chemists and physicists in the fields of polymer chemistry, polymer physics and materials science is essential.     

Molecular electronics: Current state and future trends

The paper reviews the current state of molecular electronics and considers the most interesting trends in its development. It is noted that microscopic dimensions in quantum processes are not the only advantage of molecular technology. It is also important that chemical synthesis of molecular systems ensures the identity of assembled functional elements, thereby providing reliability and efficiency of quantum processes in molecular electronic devices. We propose using the quantum effect of the Peierls instability, which is readily realized in one-dimensional molecular systems. Advantages of this approach are discussed.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 75–85, November–December, 1993.Translated by O. Kharlamova     

Analytical microextraction: current status and future trends

Analytical microextractions, defined as nonexhaustive sample preparation with a very small volume of extracting phase (microliter range or smaller) relative to the sample volume, represent an important development in the field of analytical chemistry. Analytes are extracted by a small volume of a solid or semi-solid polymeric material, as in solid-phase microextraction (SPME), or alternatively by a small volume of a liquid, as in liquid-phase microextraction (LPME). This paper gives an overview of the SPME and LPME techniques and discusses future trends. This includes a discussion of the different extraction formats available, commercial equipment, method transfer from traditional sample preparation methods to microextraction, and performance as well as robustness for the latter type of systems. In addition, the paper contains a unified approach to the understanding of extraction thermodynamics and kinetics applicable to both SPME and LPME.     

Electron transfer vs coordination chemistry: isomer-specific binding of HgII by an ortho-Wurster's thiacrown ether

Isomeric p- and o-phenylenediamine-containing macrocyclic hosts (Wurster's thiacrown ethers L1 and L2, respectively) were prepared and studied as Hg(II) ionophores. The distinct electrochemical properties of the two hosts allowed for the formation of a coordination compound with the ortho-Wurster's thiacrown ether but not the para isomer. In the latter case, the Hg(II) ion served as an oxidant in an electron-transfer reaction with the host. Solutions of the Hg(II) complex of L2 were studied by 13C NMR spectroscopy and cyclic voltammetry and revealed a strong interaction between the redox-active phenylenediamine subunit and the bound metal cation. An X-ray analysis confirmed the participation of the three macrocyclic S atoms and both phenylenediamine N atoms in the stabilization of the complex.     

Open tubular liquid chromatography: Recent advances and future trends

Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10–75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies.     

Phase behaviour and morphology from a current viewpoint

The presentation is to give an overview of polymer morphology from the standpoint of recent developments with emphasis on the underlying phase transformations. In the latter context it is essential to recognize that with the exception of special systems having complex equilibrium surfaces, the conventionally considered morphology represents a non-equilibrium state, hence a metastable state of matter arising from phase transformation having been arrested at some stage before the transformation was complete. In respect to the term ‘complete’ distinction needs to be made between completeness of material conversion and attainment of the equilibrium phase size and shape, a distinction which acquires special significance in polymeric systems as will be illustrated and discussed.     

Enantioseparations in capillary electromigration techniques: recent developments and future trends

This review summarizes the current status of enantioseparations using capillary electromigration techniques and gives the authors insights on the selected fundamental aspects and future trends in this field. The most recent developments in the field of chiral separations using capillary electrophoresis (CE) and capillary electrochromatography (CEC) are summarized. The status of chiral electromigration techniques is evaluated tacking into account the most recent developments in related techniques such as chiral HPLC, GC and SFC.     

N-H...pi interactions in pyrroles: systematic trends from the vibrational spectroscopy of clusters

Pyrrole and some of its methylated derivatives are aggregated in a controlled way in pulsed supersonic jet expansions. The cluster N-H stretching dynamics is studied using FTIR and Raman spectroscopy. Dimers, trimers and tetramers can be differentiated. Systematic trends in the dimer N-H...pi interaction as a function of methyl substitution are identified and explored for predictions. Overtone jet absorption spectroscopy is used to extract anharmonicities for the N-H bond in different environments. The N-H anharmonicity constant increases by 10% upon dimerization. Bulk matrix shifts can be emulated by the formation of Ar-decorated clusters. The experimental results are expected to serve as benchmarks for an accurate ab initio characterization of the N-H...pi hydrogen bond.     

Molecular geometry and symmetry from a differential geometry viewpoint

Relations between an earlier generalization of molecular symmetry called symmorphy and a molecular equivalence based on diffeomorphisms of electron density functional graphs (the so-called DFG equivalence introduced in our previous work) are analyzed. Any two DFG-equivalent electron density functions can be derived from one another by a suitable transformation of the spatial coordinates and the electronic charge density scale; the classes of DFG equivalence are the orbits of a group of linear operators operating in the space of electron density functions. Within the symmorphy framework, the symmetry group is derived from the symmorphy group by taking an intersection of a subgroup of the symmorphy group and the group of isometries for a natural choice of the Riemannian metric tensor. The Riemannian metric properties provide a choice for a suitable reference electron density function for each class of equivalent densities. Such reference densities serve as tools for a systematic classification of the infinite family of electron densities of molecular conformations. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64 : 669–678, 1997     

Immunoassay and other ligand assays: present status and future trends.

Immunoassay and other ligand assays have made a major impact on medical research and diagnosis since the first modern (radioisotopically-based) methods emerged. These ubiquitous microanalytic techniques are broadly classifiable as first generation (generally of "competitive" design, e.g., radioimmunoassay), and second generation (generally "noncompetitive," and relying on nonisotopic labels) these (often described as "ultrasensitive") being distinguished by dramatic improvements in sensitivity and performance time. A third generation is now in prospect (based on microarrays of antibody microspots) capable of ultrasensitive determination of hundreds of analytes in a drop of blood. Analogous technology (based on oligonucleotide arrays) is under intensive development for DNA analysis. Array technologies are likely to transform diagnostic medicine in the next decade.     

The status of process analytical instrumentation : Recommended practices and future trends

The use of process analytical instrumentation with particular reference to the oil and petrochemical industries, is reviewed, taking into account the involvement of process engineering, laboratory, operations, maintenance, and instrument engineering functions. Selection of analyzers providing process monitoring, safety control or environment protection must be based on proper appreciation of their financial contribution to process and plant operation (pay-back ratio). All aspects of the operating environment affect the operating pay-back ratio. The overall systems concept is vital. Present practices of analyzer system protection by installation in local cabinets and analyzer houses are reviewed and arguments are given for more informed practices. Construction, design, location, safety and ventilation are considered. Analyzer calibration is described in detail. Laboratory practices, maintenance procedures, maintenance training and the need for better motivation by management are discussed, as are the potential benefits of total automation. Types of process analyzers and new design and development trends are reviewed. The importance of engineering and design standards and of system and analyzer design documentation is emphasized.     

Molecularly imprinted polymers in capillary electrochromatography: recent developments and future trends

The developments in molecularly imprinted polymer (MIP)-based capillary electrochromatography (CEC) achieved during the past years are reviewed in this article. The MIP is prepared using a templated polymerization reaction and results in a material with a high selectivity towards a predetermined target. The selectivity of the MIP is comparable to that of the biological antibodies, however, the MIP is much more stable and is thus able to withstand extremely harsh conditions in terms of pH, temperature, and organic solvents. The high selectivity and stability of the MIP made it an interesting candidate for application as stationary phase sorbent in chromatography. However, due to slow kinetics the efficiency of the early MIP columns, which were predominantly applied in high-performance liquid chromatography (HPLC), were limited. The use of CEC was thought to improve the efficiency of the MIP-based separation system. The small dimensions of the capillary format employed in CEC have put demands on the polymer systems which have resulted in the development of many different polymer formats. Thus, this need for novel MIP formats for applications in CEC has contributed a lot to the general development of MIP formats as well as to the knowledge in MIP synthesis and characteristics.     

Mass spectrometry in drug metabolism and pharmacokinetics: Current trends and future perspectives

Drug Metabolism and Pharmacokinetics (DMPK) is a core scientific discipline within drug discovery and development as well as post‐marketing. It helps to design and select the most promising drug candidate and obtain advanced insights on the processes that control absorption, distribution, metabolism and excretion (ADME) of the final drug candidate. Mass spectrometry is one of the key technologies applied in DMPK. Therefore, the continuous advances made in the field of mass spectrometry also directly impact the way in which we investigate the ADME properties of a compound, providing us with new tools to gather more information or improve our efficiency. An overview will be given of some important current trends and future perspectives in the field.