Orientation of crystalline polymers by non-classical means

Crystalline polymers can be oriented by epitaxy on various substrates, including low molecular weight, usually aromatic compounds and polymers oriented by epitaxy and by mechanical means (strain induced polyolefin films and friction-deposited PTFE layers). The resulting oriented films are thin, but display unusual morphologies with lamellae standing edge-on and, often, single crystal structure. They are adequate investigation materials for structure determination, show enhanced or maximized orientation-dependent properties, and may contribute to mechanical strengthening in composite polymer films.     

Rearrangement Invariant Continuous Linear Functionals on Weak <Emphasis Type=Italic>L</Emphasis><Superscript>1</Superscript>

We show that in the dual of Weak L¹ the subspace of all rearrangement invariant continuous linear functionals is lattice isometric to a space L¹(μ) and is the linear hull of the maximal elements of the dual unit ball. We also show that the dual of Weak L¹ contains a norm closed weak* dense ideal which is lattice isometric to an ℓ¹-sum of spaces of type C(K). Helmut H. Schaefer in memoriam     

Kristall- und Molekülstruktur von Bis(pyridin)bis(trifluoromethyl)zink

Crystal and Molecular Structure of Bis(pyridine)bis(trifluoromethyl)zinc Bis(pyridin)bis(trifluoromethyl)zinc 1 has been isolated and characterized by means of single-crystal X-ray diffraction techniques. The title compound represents the first structure determination of a fully fluorinated alkylzinc compound (monoclinic, space group P2₁/c, Z = 4, a = 8.856(3), b = 18.158(3), c = 8.979(3) Å, β = 98.14(2)°, R = 0.054, R_w = 0.035). The zinc atom is in a distorted tetrahedral environment. The molecular structure of [ClZn(CCl₂CF₃) η₂O]₂ 2 was solved, but is not included in a structural comparison due to crystallographic disorder.     

Zur Berechnung der Potentialströmung um quergestellte Luftschiffkörper

Zusammenfassung Zunächst wird das v. Kármánsche Verfahren, die Potentialströmung um quergestellte Luftschiffkörper mit Hilfe einer streckenweise konstanten Dipolbelegung auf der Achse des Körpers zu berechnen, kurz skizziert und einige Überlegungen für Beginn und Ende der Belegung angestellt. Dann wird dieses Verfahren verbessert durch Annahme einer stetigen, stückweise linear veränderlichen Dipolbelegung auf der Achse. Der zweite Hauptteil der Arbeit bringt die Berechnung der Potentialströmung mit Hilfe von Quellen und Senken, die auf der Oberfläche des Luftschiffkörpers angeordnet sind. Die Integralgleichung, der diese Oberflächenbelegung genügen muß, wird angeschrieben, und der Kern auf Funktionen zurückgeführt, die sich aus vollständigen elliptischen Normalintegralen zusammensetzen lassen. Für diese Funktionen werden Diagramme gegeben. Die Integralgleichung ist durch Iteration lösbar. Die Konvergenz des Verfahrens ist gut. Zum Schluß werden die Formeln zur Berechnung der Geschwindigkeit auf der Oberfläche und des Potentials für einen beliebigen Punkt angegeben.Herrn Prof. Dr.Betz bin ich für die Anregung zu dieser Arbeit und für seine Ratschläge bei ihrer Abfassung zu besonderem Dank verpflichtet.     

Chiral 2,2-disubstituted oxirane ethers and carboxylic esters. New ferroelectric liquid crystals and dopants for induced ferroelectric phases

Abstract

The synthesis, phase behaviour and spontaneous polarization of a new class of chiral LCs and chiral dopants for induced ferroelectric phases of general structure A, possessing a (2S)-2-hydroxymethyloxirane unit, and B, possessing a (2R)-2-oxirane carboxylic acid unit connected to mesogenic building blocks are described. One of these new compounds exhibits a S*_c phase. A carbonyl group adjacent to the oxirane ring does not increase the spontaneous polarization which is in contrast to the results obtained for 2,3-disubstituted oxiranes. A comparison with analogous species containing a (2S)-2-hydroxymethyloxetane, a (2R)-2-hydroxymethylthiirane or a (2S,3R)-2-hydroxymethyloxirane unit is given.     

Synthesis, characterization, and structural studies of multimetallic ferrocenyl carbene complexes of group VII transition metals

Fischer carbene complexes of the group VII transition metals (Mn and Re) containing at least two or three different transition metal substituents, all in electronic contact with the carbene carbon atom, were synthesized. The structural features and their relevance to bonding in the carbene multimetal compounds were investigated, as they represent indicators of possible reactivity sites in polymetallic carbene assemblies. For complexes of the type [ML(x){C(OR)R'}] (ML(x) = MnCp(CO)(2) or Re(2)(CO)(9)), ferrocenyl (Fc) was chosen as the R' substituent, while the OR substituent was systematically varied between an ethoxy or a titanoxy group, to yield the complexes 1a (ML(x) = MnCp(CO)(2), R = Et, R' = Fc), 2a (ML(x) = MnCp(CO)(2), R = TiCp(2)Cl, R' = Fc), 3a (ML(x) = Re(2)(CO)(9), R = Et, R' = Fc), and 4a (ML(x) = Re(2)(CO)(9), R = TiCp(2)Cl, R' = Fc). Direct lithiation of the ferrocene with n-BuLi/TMEDA at elevated temperatures, followed by the Fischer method of carbene preparation, resulted in formation of the novel biscarbene complexes with bridging ferrocen-1,1'-diyl (Fc') substituents [{π-Fe(C(5)H(4))(2)-C,C'}{C(OEt)ML(x)}(2)] (1b, ML(x) = MnCp(CO)(2); 3b, ML(x) = Re(2)(CO)(9)) or the unusual bimetallacyclic bridged biscarbene complexes [{π-TiCp(2)O(2)-O,O'}{π-Fe(C(5)H(4))(2)-C,C'}{CML(x)}(2)] (2b, ML(x) = MnCp(CO)(2); 4b, ML(x) = Re(2)(CO)(9)). The target compounds that were isolated displayed a variety of different geometric isomers and conformations. The greater reactivity of the binary dirhenium acylates in solution, compared to that of the cyclopentadienyl manganese acylate, resulted in a complex reaction mixture. Although the stabilization of hydroxycarbene or hydrido-acyl intermediates of dirhenium carbonyls could not be achieved, their existence in solution was confirmed by the isolation of [(π-H)(2)-(Re(CO)(4){C(O)Fc})(2)] (8), the unique dichloro-bridged biscarbene complex fac-[(π-Cl)(2)-(Re(CO)(3){C(OEt)Fc})(2)] (6), the known hydrido complex [Re(3)(CO)(14)H] (5), the acyl complex [Re(CO)(5){C(O)Fc}] (7), and the aldehyde-functionalized eq-[Re(2)(CO)(9){C(OTiCp(2)Cl)(Fc'CHO)}] (9).     

The synthesis, structural features and thermal behaviour of thiophene-containing dithiocarboxylate complexes of zinc(II)

The complexes [Zn₂(S₂CTR)₄] (T = 2,5-disubstituted thiophene, R = C₄H₉ (1), C₆H₁₃ (2), C₈H₁₇ (3), C₁₂H₂₅ (4) and C₁₆H₃₃ (5)) have been synthesized and their structural features investigated. Compared to the analogous dithiobenzoate complexes, the crystal structure determination of 2 revealed that the thiophene induces a “step-rod” chain pattern instead of the linear, rodlike structure found for the corresponding dithiobenzoates. Complexes 1–5 did not display mesophases under thermal conditions, but an irregular melting pattern was observed for 3 and 4.     

Herstellung und Beständigkeit im aromatischen Kern substituierter 1.3-Benzodioxane

Zusammenfassung Es werden 1.3-Benzodioxanderivate hergestellt, die in 6-Stellung Alkoxycarbonyl- oder Carboxylgruppen, einige außerdem in der 8-Stellung Chlor, Brom oder eine Benzylgruppe enthalten. Bei der Hydrolyse der halogensubstituierten Benzodioxane mit konz. Salzsäure werden Dihydroxydiphenylmethanderivate erhalten.

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Preparation and stability of 1.3-benzodioxanes substituted in the benzene ring

Derivatives of 1.3-benzodioxane are prepared with alkoxycarbonyl or carboxyl groups in position 6 and to some extent with chlorine, bromine or a benzyl group in position 8. The hydrolysis by conc. hydrogen chloride of the substances substituted with halogen gives derivatives of dihydroxydiphenylmethane.

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Benzodioxane in: Heterocyclic compounds, Vol. 6, p. 59 (R. C. Elderfield, ed.), New York: Wiley. 1957.     

The probability that a slightly perturbed numerical analysis problem is difficult

We prove a general theorem providing smoothed analysis estimates for conic condition numbers of problems of numerical analysis. Our probability estimates depend only on geometric invariants of the corresponding sets of ill-posed inputs. Several applications to linear and polynomial equation solving show that the estimates obtained in this way are easy to derive and quite accurate. The main theorem is based on a volume estimate of -tubular neighborhoods around a real algebraic subvariety of a sphere, intersected with a spherical disk of radius . Besides and , this bound depends only on the dimension of the sphere and on the degree of the defining equations.