Propriétés des copolymères biséquencés polyoxyéthylène-polystyrène

Résumé On a préparé des monocristaux de copolymères biséquencés polyoxyéthylène-polystyrène (POE-PS) à partir de leurs solutions diluées, qui peuvent contenir jusqu'à 55% de PS. Les principales formes de ces cristaux et leurs variantes morphologiques, observées sous microscope optique, sont décrites et rattachées à la maille cristallographique du POE. On présente aussi quelques exemples de monocristaux obtenus par ensemencement, dans lesquels les différentes formes se succèdent par filiation; on discute les transitions des formes et leur dépendance vis à vis des conditions de cristallisation.La cristallisation de ces copolymères provoque généralement un fractionnement en composition, car la proportion de PS dans les cristaux est limitée. On propose deux modèles de structure différents, dans lesquels une ou deux couches cristallines de POE en configuration repliée sont recouvertes par le PS amorphe. Le processus de fractionnement est interprété à partir de ces deux structures en admettant une extension critique pour les séquences de PS, dont l'une des extrémités est ancrée sur la surface des repliements du POE.

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Summary Single crystals of copolymers, composed of one Poly(ethylene-oxide), (POE), and one Polystyrene (PS) block, (which may contain 55% of PS, by weight), have been prepared from dilute solutions. The principal crystal habits and their morphological variations, as observed with an optical microscope, are described and related to the unit cell of POE. Single crystals grown from various types of seeds, in which different external habits succeed one another, are also shown. Transitions of crystal habits and their dependence on crystallisation conditions are discussed in some detail.Generally, crystallisation of these copolymers produces some fractionation with respect to composition, for only a limited fraction of the initial PS can enter into the crystal. Two different crystal structures are proposed in which a single, or a double crystalline layer of folded POE is covered by amorphous PS. The fractionation process is interpreted on the basis of these two structural models, assuming a critical extension of the PS blocks anchored at one end to the fold surface of PEO.

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Zusammenfassung Einkristalle von Copolymeren aus einem Polyäthylenoxyd (PEO) und Polystyrol (PS)-Block, die gewichtsmäßig 55% PS enthalten können, wurden aus verdünnten Lösungen präpariert. Der grundsätzliche Charakter der Kristalle und ihre morphologischen Variationen, wie es in einem optischen Mikroskop beobachtet wird, ist beschrieben und mit der Elementarzelle PEO in Beziehung gebracht. Einkristalle, entstanden aus verschiedenen Typen von Kristallkeimen, in welchen verschiedene äußere Formen auftreten, die aufeinanderfolgen, werden gezeigt. Die übrigen Kristallformen und ihre Abhängigkeit von den Kristallisationsbedingungen werden im einzelnen diskutiert.Im allgemeinen verursacht die Kristallisation dieser Copolymeren gewisse Fraktionierung hinsichtlich der Zusammensetzung, da nur eine begrenzte Menge des ursprünglichen Polystyrols in den Kristall eintreten kann. Zwei verschiedene Kristall-Strukturen werden vorgeschlagen, in denen bzw. eine oder zwei Schichten von gefaltetem PEO mit amorphem Polystyrol bedeckt ist. Der Fraktionierungsprozeß wird auf Grund dieser zwei Struktur-Modelle interpretiert, die eine kritische Größe der PS-Blöcke, verankert an einem Ende der gefalteten Oberfläche von PEO, annehmen.

     

Photothermochemical process in ammonium perchlorate crystals: II

The influence of phase transition (PT) on the process of thermal development of a latent image arising after X-ray and uv irradiation of ammonium perchlorate (AP) crystals has been studied. Despite the production of a large number of new dislocations accompanying PT, it essentially does not influence the thermal development: The developed image does not smear at PT, remaining as clear as before it. By comparing mirror-symmetric surfaces of cleavage planes of AP crystals, it has been shown that at doses of X-ray and uv irradiation sufficient for obtaining an image, no production of new dislocations was observed in AP crystals. It is suggested that latent image arises due to formation during irradiation of chlorine oxidic products of radiolysis: ClO₃, ClO₂, and ClO as well as the corresponding ions ClO^?, ClO^?₂, and ClO^?₃, i.e., initiators of AP low-temperature decomposition.     

Structure and properties of 2,4a-dimethyl-4-phenyl-3-ethoxycarbonyl-5-oxo-4a,5-dihydro-4H-indeno[1,2-b]pyridine

The molecular and crystal structure of 2,3a-dimethyl-4-phenyl-3-ethoxycarbony-5-oxo-4a,5-dihydro-4H-indeno[1,2-b]pyridine has been determined, and its reduction and alkaline and acid hydrolysis reactions have been studied.Translated from Khimiya Geterotsiklicheskikh Soedineii, No. 10, pp. 1388–1392, October, 1984.     

Beiträge zur Chemie der Pyrrolpigmente, 9. Mitt.: Bildung,Struktur und Konfiguration vonZ- undE-Arylmethyliden-3,4-dimethyl-3-pyrrolin-2-onen

The condensation of 3.4-dimethyl-3-pyrrolin-2-one with p-methyl-, p-chloro-benzaldehyde and ferrocenealdehyde yields theZ-andE-isomers of the corresponding condensates. Due to kinetic control theZ-isomers are obtained almost exclusively in this reaction. TheE-isomers of the two firstmentioned products can be produced by photochemical isomerization. The structures (tautomeric forms) and configurations of the isomers were established by the Lanthanide-induced-shift-technique and by evaluating the Nuclear-Overhauser-Effect.     

Kinetics of the reaction between phenylacetylene and the complex of decaborane with diethyl sulfide

Conclusions The manometric method was used to study the kinetics of the reaction of phenylacetylene with the complex of decaborane and diethyl sulfide, with the formation of 1-phenyl-o-carborane. The reaction is described by a second order equation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1818, August, 1971.     

A study of certain complex compounds of iron with the aid of magnetic measurements and the method of nuclearγ-resonance

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