Synthesis of micron-sized, monodisperse polymer particles of disc-like and polyhedral shapes by seeded dispersion polymerization

Micron-sized, monodisperse polymer particles having unique disc-like and polyhedral shapes were produced by seeded dispersion polymerization of various methacrylates with 1.57 m-sized polystyrene seed particles in the presence of saturated hydrocarbon droplets in methanol/water. Such nonspherical shapes were controllable by the polymerization conditions.Part CCLX of the series Studies on Suspension and Emulsion     

Thermal analysis of macromolecules

This review traces the development of thermal analysis over the last 40 years as it was experienced and contributed to by the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential scanning calorimetry (DSC), single run DSC and other special instrumentations, up to the recent addition of modulation to calorimetry. Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied interests one can have over 40 years. It began with cold crystallization and most recently the term oriented, intermediate phase was coined, creating in-between: extended chain crystals, the irreversible thermodynamics of melting of polymer crystals, dynamic differential thermal analysis (DDTA), the rule of constant increase ofC _p per mobile bead within a molecule at the glass transition temperature, superheating of polymer crystals, melting kinetics, crystallization during polymerization, the chain-folding principle, molecular nucleation, rigid amorphous phase, a system of classifying molecules, macroconformations, amorphous defects, rules for the entropy of fusion based on molecular shape and flexibility, single-molecule single-crystals, a system of classifying phases and mesophases, and condis phase.First and foremost I would like to acknowledge the unwavering support through my wife, Heidel, without whom many of the projects simply could not have been completed. Similarly, our children had to grow up knowing that often research and teaching had to take precedence. Without coworkers, little could have been accomplished. Of the about 120 postdoctoral fellows, graduate students, and technicians, most of whom contributed to the listed references, and many have participated on their own in this issue, goes my thanks for the bulk of the scientific work. Many friends and colleagues contributed with discussion and constructive criticism, some of them have also contributed in this collection of papers related to thermal analysis. Little work can be done without this interplay of ideas. The limited space has not permitted to give a full appreciation of the importance of the ideas drawn from the literature. These thousands of additional references can be found in the initial papers and reviews of the subjects treated.Material support was received from the three major instrument companies for thermal analysis equipment: TA Instruments, Inc.; Perkin-Elmer Corp.; and Mettler-Toledo, Inc. Without this help we would not always have been able to be at the forefront of instrumentation. Major financial support for the research came from outside the universities. I estimate that over the 40 years about 4 Megadollars were spent by government agencies, companies, and private foundations to support coworkers, myself during the summers, research equipment, expenses, and travel. A large amount of money, but not too much if one compares it to typical expenditures in the field of athletics (about 10 k$ per paper). Major sustained funding came from the Advanced Projects Agency (ARPA), the Office of Naval Research (ONR), the National Aeronautics and Space Agency (NASA), the Department of Energy (DOE), and, most prominently, the National Science Foundation (NSF). At present our work is supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc. Industrial support is presently given by TA Instruments, Inc; ICI Paints; Exxon Res. and Eng. Co.; Shell Development Co.; Toray Research Center; and Mettler-Toledo, Inc.Last, but by no means least, I would like to thank Dr. E. Turi for the invitation to write this paper and for her untiring effort to entice so many of my students and friends to contribute to this issue of the Journal of Thermal Analysis.     

Zur Frage des Einsatzes ionenspezifischer Elektroden in der Automation

Zusammenfassung Es wurden Untersuchungen mit anionenspezifischen Membranelektroden nach Pungor durchgeführt. Dazu werden Reproduzierbarkeit, Eichfunktion, Einstellzeiten bei auf- und absteigender Konzentration und Querempfindlichkeit im Hinblick auf den Einsatz in automatischen Systemen behandelt. Es wird vorgeschlagen, für die Angabe der Selektivität einen p-Sel analog zum pH zu verwenden, die Behandlung eines Analysensensorsystems wird vorgenommen.

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On the use of ion-specific electrodes in automation

Investigations on anion-specific membrane electrodes are described. Problems of reproducibility, calibration, time-response in respect of in- and decreasing concentrations and sensitivity to interfering ions are demonstrated and discussed with regard to automation. It is proposed to define a p-sel for the selectivity constant analogue to pH and a calculation method for an Analysis-Sensor-System is shown.

     

Theoretical conformational analysis of cyclic hexadepsipeptides. Enniatins

Conclusions The spatial conformation of the polar form of enniatin B has been established. A conformation of the N₁ type has been proposed for the nonpolar form.Institute of the Chemistry of Natural Compounds, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 616–622, September–October, 1970.     

Eine Mikromethode zur Bestimmung von Zink in Serum mittels flammenloser Atomabsorption

Zusammenfassung Eine Mikromethode zur Bestimmung von Zink in kleinsten Serummengen mittels flammenloser Atomabsorption wurde beschrieben. Zur Verdünnung der Serumproben wird eine Tris-Lösung verwendet. Um eine Angleichung von wäßrigem Standard und Proben zu erreichen, wird durch Zugabe eines Kationenaustauschers zu einem Mischserum ein zinkarmes Matrixserum hergestellt.

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Microdetermination of zinc in human serum

Summary A micromethod for determination of zinc in small amounts of human serum is described. For dilution of serum samples a solution of tris is used. To match aqueous standards and samples, pooled serum from the clinical laboratory is treated with a cation exchange resin to give a low zinc matrix serum.

     

Metal concentrations in scleractinean corals determined by instrumental neutron activation analysis and atomic absorption spectrometry

Five species of scleractinean corals, extracted from the Northern Havana reef, were studied by INAA and AAS. Selected specimens were sectioned in foot, center and head parts before pulverization procedure. INAA for different irradiation and decay time regimes in a reactor allowed the determination of: Na, Mg, Al, Cl, Sc, Cr, Co, Th, Lu, Eu, Ce, Hf, La and Sr. AAS was performed in a Pye Unicam Model 929 spectrometer. Cu, Mn, Ni, Zn, and Fe were detected. Ca concentration in all species was also established. Obtained Metal-Calcium ratios for Sr, Cu, Zn, Cr, Co, Fe, Mn, Ni and Sc are compared with reported values.     

Der o-Effekt in den Massenspektren aromatischer Verbindungen

Zusammenfassung Das Massenspektrum des O-Äthylsalicylsäureamides VII b ist von dem seiner m- und p-isomeren Verbindung völlig verschieden und zeigt einen typischen massenspektrometrischen o-Effekt.Die bisher aufgefundenen Verbindungen mit massenspektro-metrischem o-Effekt gehören einem relativ kleinen Kreis von Aromaten mit ganz bestimmten Strukturmerkmalen an. Die Bildung der für den o-Effekt charakteristischen Bruchstücke kann in allen diesen Fällen nach einem vonMcLafferty aufgestellten Mechanismus zwanglos erklärt werden. Verbindung VIIb hätte unter der Voraussetzung, daß eine Entstehung der für den o-Effekt typischen Fragmente nur nach diesem Mechanismus möglich ist, keinen o-Effekt zeigen dürfen.Das Auftreten des o-Effektes im Massenspektrum von VIIb läßt erkennen, daß die Bedingung zur Bildung der für den o-Effekt charakteristischen Bruchstücke lediglich in der Möglichkeit zur Ausbildung stabiler Spaltprodukte zu suchen ist, und daß daher weit mehr Verbindungen einen o-Effekt zeigen sollten als bisher anzunehmen war.Mit 1 Abbildung     

The electronic structure of the boron hydrides

In parts I and II of this series [1] it has been demonstrated that localized three centre and two centre bonds may be used as basic functions for molecular orbital calculations on closed (cage) and open (basket) boron polyhedral molecules. In the present paper it is shown that the face and edge matrices of this theory are related to incidal and 1 and 2 simplexial matrices in the same way that Hückel matrices in the theory of unsaturated hydrocarbons are related to incidal matrices and 0 and 1 simplexial matrices. The theory is thus a topologically-correct extension of Hückel theory to three dimensions.

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Zusammenfassung In Teil I und II dieser Serie [1] wurde demonstriert, da\ lokalisierte Dreizentren- und Zweizentren-Bindungen als Basisfunktionen für MO-Rechnungen bei geschlossenen (KÄfig) und offenen (Korb) polyhedralen Borwasserstoff-Molekülen benutzt werden können. In der vorliegenden Arbeit wird gezeigt, da\ die OberflÄchen- und Randmatrizen dieser Theorie mit Incidal- sowie 1- und 2-Simplexmatrizen verwandt sind, in derselben Art wie die Hückel-Matrizen in der Theorie der ungesÄttigten Kohlenwasserstoffe mit Incidal-Matrizen sowie 0- und 1-Simplexmatrizen in Beziehung stehen. Die Theorie ist somit eine topologisch korrekte Erweiterung der Hückel-Theorie auf drei Dimensionen.

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Résumé Dans les parties I et II de cette suite d'articles on a démontré que des liaisons localisées à trois et à deux centres peuvent Être employées comme fonctions de base pour des calculs d'orbitales moléculaires sur des molécules polyhédriques boriques fermées («cage») et ouvertes («panier»). Dans cet article on montre que les matrices «faces» et «arÊtes» de cette théorie sont liées aux matrices d'incidence et aux matrices Simplexes 1 et 2 de la mÊme manière que dans la théorie de Hückel la matrice hamiltonienne est reliée aux matrices d'incidence et simplexes 0 et 1. La théorie est donc une extension à trois dimensions, correcte du point de vue topologique, de la méthode de Hückel.

     

Preparation and analysis of a river sediment Standard Reference Material for the determination of trace organic constituents

Summary A river sediment Standard Reference Material (SRM) has been prepared and analyzed for determination of the concentrations of trace organic constituents. SRM 1939, Polychlorinated Biphenyls (PCBs) in River Sediment A, has been certified for the concentrations of three PCB congeners using the results obtained from capillary column gas chromatography with electron capture detection (GC-ECD) and from multidimensional (dual column) capillary gas chromatography with mass spectrometric detection (MCGC-MSD). For SRM certification, two independent analytical procedures are usually required. If only one analytical technique is used or if the procedures are not independent, then the concentrations are reported as noncertified or informational values rather than certified values. Noncertified values for 14 additional PCB congeners and five chlorinated pesticides, determined by GC-ECD, are also reported as well as noncertified concentrations for five polycyclic aromatic hydrocarbons (PAHs), determined using gas chromatography with mass spectrometric detection (GC-MSD). SRM 1939 complements SRM 1941, Organics in Marine Sediment, since both materials have 12 PCB congeners, five PAHs and five chlorinated pesticides in common. However, the concentrations differ by an order of magnitude for PAHs, and from one to over two orders of magnitude for the PCB congeners and chlorinated pesticides.     

A comparison of techniques for embedding defect cluster calculations

Cluster calculations have proved one of the most fruitful means of extracting useful information about solid-state defect properties at finite computational expense, but large clusters are necessary to obtain reliable results and uncertainty always remains concerning the effects of edge states, with ad hoc boundary conditions such as the saturation of the surface with hydrogen atoms being frequently employed. Recently methods have been developed for embedding the cluster in the perfect crystal so that the solution obtained from the cluster calculation is the same as would have been obtained from a full calculation on the whole defective solid. Here the relationships of these methods with each other and with perturbed crystal methods which modify the perfect crystal solution to account for the presence of the defect are explored. It is shown that the embedding potential technique is preferable and is equivalent to methods that have been used in other fields.This paper was presented at the International Conference on The Impact of Supercomputers on Chemistry, held at the University of London, London, UK, 13–16 April 1987     

The Story of Nitinol: The Serendipitous Discovery of the Memory Metal and Its Applications

The shape-retaining alloy Nitinol (Nickel Titanium Naval Ordance Laboratory), the metal with a memory, is revolutionizing manufacturing, engineering, and medicine as countless products that think for themselves enter the marketplace. This article recounts its discovery in 1959 by William J. Buehler of the U.S. Naval Ordnance Laboratory, its subsequent development by Buehler and Frederick E. Wang, and its applications in orthopedic and cardiovascular surger, orthodontics, solid-state heat engines, shrink-to-fit pipe couplers for aircraft, safety products, eyeglass frames, and toys. The serendipitous nature of the discovery, the solid-to-solid (austenite to martensite) phase transition that produces the alloys unusual properties, its numbers practical applications, and the ready availability of samples make the alloy an ideal, exiting, and thought-provoking topic for cheistry course at all levels in both lecture and laboratory.     

Determination of polychlorobiphenyls and polycyclic aromatic hydrocarbons in the atmospheric aerosol of the Venice Lagoon

An analytical method for simultaneous determination of particle-associated and gaseous-phase concentrations of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) in atmospheric aerosol samples obtained by high-volume samplers using polyurethane foam adsorbent (PUF) and quartz fibber filters (QFF) has been investigated. Quality control of the analytical procedure was carried out by blank control and by evaluating limits of detection, recoveries, accuracy, and repeatability. The proposed method was subsequently used to determine PAH and PCB in the gaseous and particulate phases of the aerosols that enter the Venice Lagoon atmosphere. The highest concentrations of PCB and PAH were predominantly in the gaseous phase. In both particulate and gaseous phases the penta-CB congeners dominated total PCB concentrations whereas phenanthrene, fluoranthene, and pyrene dominated the PAH concentrations. Total (gaseous plus particulate) PCB and PAH concentrations were higher at the site directly influenced by the industrial plants but the concentrations in marine aerosol samples were lower by a factor four only and must be taken into consideration when studying the chemical contamination of the Venice Lagoon.     

Interplay of Thermochemistry and Structural Chemistry, the Journal (Volume 11, 2000), and the Discipline

As practiced disciplines, structural chemistry and thermochemistry need not be related. In the current study they are: the entire contents of the journal Structural Chemistry (Vol. 11) for the year 2000 has been reviewed and then each and every article that appeared therein was given a thermochemical commentary, spin or slant.     

Configuration analysis and electronic states properties

The excited-states electronic properties of unsaturated small-ring hydrocarbons with four- and six--electrons have been studied by the Molecules in Molecules method and compared with experimental data and PPP results interpreted through a configuration analysis procedure. The results show that the MIM method is applicable with good reliability.

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Zusammenfassung Die elektronischen Eigenschaften der angeregten Zustände von ungesättigten kleinen Kohlenwasserstoffringen mit vier und sechs -Elektronen wurden mit Hilfe der Molekül- im-Molekül-Methode untersucht und die Ergebnisse mit experimentellen Daten und PPP Resultaten, die durch eine Konfigurationsanalyse interpretiert wurden, verglichen. Die Ergebnisse zeigen, daß die MIM-Methode mit großer Zuverlässigkeit anwendbar ist.

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Financial aid from the Italian C.N.R. is gratefully acknowledged.     

X-ray structural analysis of tetrahydrofurofuran lignans

The crystal structures of two diastereomeric tetrahydrofurofuran lignans, diasesartemin (1) and episesartemin-B (2), were determined. The former one is of the classical axial-axial substitution type (the two aryl moieties of the 1,4-diaryl-tetrahydro-1H,3H-furo[3,4-c]furan in ax-ax position), the latter one belongs to the axial-equatorial type. Analysis of the X-ray results revealed that in both cases the substituents are attached in pseudo-equatorial positions due to a flip of the (slightly twisted) envelope conformation of the oxolane five-rings. In1 the oxygen atoms of the two five rings point against each other (overall boat conformation of the tetrahydrofurofuran system orendo-endo topology), in2 one ring is folded towards and the other one is folded away from the second ring (overall boat-chair conformation of the tetrahydrofurofuran system orendo-exo topology): as a consequence,all aryl substituents adopt a pseudo-equatorial position. The terms ax-ax, ax-eq, and eq-eq used throughout in the literature are therefore misleading as far as the true conformations are concerned. Analysis of the aromatic short wavelength CD couplet of1 by means of the coupled oscillator model shows that the X-ray derived geometry is compatible with the CD data in solution.

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Röntgenstrukturanalyse von Tetrahydrofurofuran-Lignanen

Zusammenfassung Es wurde die Kristallstruktur von zwei diastereomeren Tetrahydrofurofuran-Lignanen, Diasesartemin (1) und Episesartemin-B (2), bestimmt. Ersteres gehört dem klassischen axial-axial-substituierten Typ an (dabei sind die zwei Arylsubstituenten des 1,4-Diaryl-tetrahydro-1H,3H-furo[3,4-c]furans in ax-ax-Position), das zweite gehört zum axial-equatorial-Typ. Die Röntgenstrukturanalyse zeigte, daß die Aryl-Substituenten immer in pseudo-equatorialen Positionen stehen, da die Oxolan-Fünfringe eine entsprechende (leicht getwistete) Briefumschlag-Konformation einnehmen. In1 zeigen die Sauerstoffatome der beiden Ringe zueinander (insgesamt eine Boot-Konformation des Tetrahydrofurofuransystems bzw.endo-endo-Topologie), in2 ist ein Ring in Richtung zum, der andere Ring jedoch weg vom jeweils zweiten gegenüberliegenden gefaltet (insgesamt eine Boot-Sessel-Anordnung in der Tetrahydrofurofuran-Einheit bzw.endo-exo-Topologie): Eine Folge davon ist, daß alle Arylsubstituenten eine pseudo-equatoriale Position einnehmen. Die in der Literatur durchgehend verwendete Bezeichnung ax-ax, ax-eq oder eq-eq ist daher bezüglich der tatsächlichen Konformation mißverständlich. Die Analyse der kurzwelligen aromatischen CD-Banden von1 mittels des Modells der gekoppelten Oszillatoren zeigte, daß die Konformation aus der Röntgenstrukturanalyse mit den CD-Daten in Lösung in Übereinstimmung ist.

     

Theoretical am1 studies of inclusion complexes of α- and β-cyclodextrins with methylated benzoic acids and phenol,and γ-cyclodextrin with buckminsterfullerene

Semiempirical AM1 calculations have been performed on the inclusion complexes of - and -cyclodextrin with benzoic acid and phenol and -cyclodextrin with methylated benzoic acids in the head first and tail first positions. The results show that -cyclodextrin complexes with phenol and benzoic acid guests in the head first position are more stable than in the tail first position, while -cyclodextrin complexes with the same guests prefer the tail first position. The preferred orientation for -cyclodextrin with methylated benzoic acids is determined by the position of the methyl substituent(s). In general, para-methyl benzoic acid derivatives prefer the tail first position. -cyclodextrin forms a slightly unstable 1:1 complex with C₆₀ (3.4 kcal/mol), but two -cyclodextrins provide enough stabilization by about 10 kcal/mol to cage-in the C₆₀.     

Formation mechanism of an “onionlike” multilayered structure by reconstruction of the morphology of micron-sized,monodisperse poly(methyl methacrylate)/polystyrene composite particles with the solvent-absorbing/solvent-releasing method

The formation mechanism of the onionlike multilayered morphology of micron-sized, monodisperse poly(methyl methacrylate) (PMMA)/polystyrene (PS) (1/1 w/w) composite particles by the solvent-absorbing/solvent-releasing method was discussed. It was concluded that the orientation of PMMA components at the outer interface of toluene-swollen particles with water is the trigger and that PMMA-g-PS operates to stabilize inner multilayer interfaces for the formation of the onionlike multilayered morphology.Part CCLV of the series Studies on suspension and emulsion     

Computer-aided library search of combined LC-Retention and diode-array-UV-spectral data

An automated library search system for computer-aided identification of organic compounds using combined UV-spectral and LC-retention data, as acquired by HPLC with linear diodearray-UV-detection, is presented.The keystone of the system is a set of similarity indices which have been developed on the basis of mathematical-statistical models of the reproducibility of the spectral and retention data. The similarity indices have the form of a significance probability, a quantity originating from the general theory of hypothesis testing. The output of the LC-UV retrieval system is a compound identity or a list of identities (if any) for which the relevant similarity index has a value above a preset threshold. The data base used in this investigation contained 186 sets of UV-spectral and LC-retention data of 74 organophosphorus pesticides measured from standard solutions under various experimental conditions. A test set consisted of 186 alternative data sets of the same compounds as contained in the data base, however measured under different experimental conditions. The performance of the LC-UV reproducibility-based retrieval (LUVRR) system was evaluated using recall/reliability plots. The results appeared to be quite promising: for 95% of the unknowns, the target reference (correct positive) was on top of the hit list with a similarity index value being significantly higher than values found for false positives.The software is written in Pascal. The present (experimental) version of the system runs on a Data General Eclipse MV/4000 minicomputer.     

High-speed analysis for acid-rain anions by Single-Column Ion Chromatography (SCIC)

Summary Single Column Ion Chromatography (SCIC) combines ion exchange separation with direct electrical conductivity detection. Because no supressor column is used in SCIC the post-column dead volume is minimized. This means that HPLC technology can be applied to reduce analysis times. The analysis of chloride, nitrate, and sulphate can be accomplished in 6 min using a standard 250×4.6 mm LC column packed with a low-capacity ion-exchange chemically bonded silica leading to a sensitivity of 100 ppb. A 1 min analysis for chloride, nitrate, and sulphate at the ppm level is possible using a 30×4.6 mm column eluted with 4mM phthalate buffer at pH 4.5.Presented at the 14th International Symposium on Chromatography London, September, 1982     

The physical crosslinking of polyurethane elastomers studied by X-ray investigation of model urethanes

Polyurethane elastomers extended with aliphatic glycols or diamines, show a characteristic fluctuation in their thermal and hydrothermal properties which is dependent on the number of CH₂ groups in the chain extender (even or odd).The causes of this behavior are examined in the following report using X-ray crystallographic analyses of single crystals of model urethanes. These model compounds were prepared by reaction between diphenylmethane -4-mono-isocyanate and glycoles of the HO-(CH₂)_n-OH structure withn=2 to 6.Whilst strain-free hydrogen bonds can form between neighboring molecules in urethanes with even chain extenders, significant strains occur in urethanes containing odd chain extenders which result in reduced stability of the physical crosslinking system.In memoriam to Prof. Dr. Dr. h. c. mult. Otto Bayer.