Poly(carbon suboxide): A photosensitive paramagnetic ladder polymer

Yang, Nan‐Loh; Snow, Arthur W.; Haubenstock, H.; Bramwell, Fitzgerald B.

doi:10.1002/pol.1978.170160811

Cited by 19 publications

(22 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In reality, the observed energy release is apparently associated with the transition of the CO polymerized phase to an equilibrium state of the mixture of CO 2 and solid carbon (these are precisely the products found after the annealing of polymer CO). Note that the pattern of non-equilibrium transformations under pressure of the CO molecular phase can be more complicated; in particular, under pressure a disproportionation is possible of the CO compound into C 2 O 3 and C 3 O 2 modifications which, in turn, are polymerized [19,20,21]. In any event the polymerization of CO under pressure is a non-equilibrium transformation to a more low-laying energy state similar to the polymerization of acetylene C 2 H 2 and benzene C 6 H 6 under pressure.…”

mentioning

confidence: 99%

Metastable phases and ‘metastable’ phase diagrams

Бражкин

2006

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

The work discusses specifics of phase transitions for metastable states of substances. The objects of condensed media physics are primarily equilibrium states of substances with metastable phases viewed as an exception, while the overwhelming majority of organic substances investigated in chemistry are metastable. It turns out that at normal pressure many of simple molecular compounds based on light elements (these include: most hydrocarbons; nitrogen oxides, hydrates, and carbides; carbon oxide (CO); alcohols, glycerin etc) are metastable substances too, i.e. they do not match the Gibbs' free energy minimum for a given chemical composition. At moderate temperatures and pressures, the phase transitions for given metastable phases throughout the entire experimentally accessible time range are reversible with the equilibrium thermodynamics laws obeyed. At sufficiently high pressures (1-10 GPa), most of molecular phases irreversibly transform to more energy efficient polymerized phases, both stable and metastable. These transformations are not consistent with the equality of the Gibbs' free energies between the phases before and after the transition, i.e. they are not phase transitions in "classical" meaning. The resulting polymeric phases at normal pressure can exist at temperatures above the melting one for the initial metastable molecular phase. Striking examples of such polymers are polyethylene and a polymerized modification of CO. Many of energy-intermediate polymeric phases can apparently be synthesized by the "classical" chemistry techniques at normal pressure. 1. The phase transition effect falls equally within the area of both physical and chemical studies. The notion of the "phase" of was introduced by J.W. Gibbs [1] as a condition of substance with a certain "phase", meaning a set of pulses and coordinates of the particles (atoms or molecules) that make up the substance. At a later time, the meanings of the term "phase" evolved so that currently the definitions of the phase of a substance used in physics and chemistry literature are somewhat different [1,2,3,4,5,6]. In chemistry the thermodynamic equilibrium condition is not mandatory for the phase. In physics the thermodynamic non-equilibrium is allowed in principle but with reservations of the kind as in [2] "sometimes the non-equilibrium metastable state of a substance is also called the "phase (metastable phase)". This seemingly minor distinction in the definitions accepted in physics and chemistry has a profound meaning. An incomplete understanding of the specifics of metastable molecular organic and inorganic compounds often gives rise to an erroneous interpretation of experimental data on phase transitions in these systems. In the present paper, the focus of our attention is the analysis of quasi-equilibrium and non-equilibrium phase transformations in metastable phases.The name "metastable phase" is given to a nonequilibrium state of a substance whose properties change reversibly over a period of the experiment or observation. Strictly speaking,...

show abstract

mentioning

confidence: 99%

Metastable phases and ‘metastable’ phase diagrams

Бражкин

2006

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

show abstract

“…The highest yields have been achieved via thermolysis of the malonic acid bistrimethylsilylester on P 4 O 10 at 160 8C. [6] The polymer (C 3 O 2 ) x can be obtained by chemical vapor deposition from the gas-phase, [7][8][9][10] via gamma-ray initiation from the solid [11,12] or by using different means of initiating the polymerization reaction from liquid phase. [12][13][14] The polymerization occurs even without adding a starting agent.…”

Section: Introductionmentioning

confidence: 99%

“…[17,18] The activation energies vary with different surface materials from 1.5 to 2.4 kJ mol À1 . [7,13,17] A very difficult issue is the elucidation of the molecular structure of poly(carbonsuboxide)s. Their amorphous character and insolubility in many organic solvents are the main reasons why so many contradictory structural models can be found in the literature. [10,12,14,18,19] Even worse, there are indications that poly(carbonsuboxide) polymers with different molecular structure do exist.…”

mentioning

confidence: 99%

“…[7,13,17] A very difficult issue is the elucidation of the molecular structure of poly(carbonsuboxide)s. Their amorphous character and insolubility in many organic solvents are the main reasons why so many contradictory structural models can be found in the literature. [10,12,14,18,19] Even worse, there are indications that poly(carbonsuboxide) polymers with different molecular structure do exist. An early model suggested by Diels described the polymer as a spiropolycyclobutadione, [15] Ziegler [20] described the structure as a poly-a-pyrone, Boehm et al [14] suggested a single planar molecule formed by about 15 monomers units and Paiaro et al [12] polymers based on poly-g-pyrone or a mixed a-pyrone and g-pyrone backbone, respectively.…”

mentioning

confidence: 99%

See 1 more Smart Citation

The Structure of Poly(carbonsuboxide) on the Atomic Scale: A Solid‐State NMR Study

Günne

Beck

Hoffbauer

et al. 2005

Chemistry A European J

View full text Add to dashboard Cite

In this contribution we present a study of the structure of amorphous poly(carbonsuboxide) (C3O2)x by 13C solid-state NMR spectroscopy supported by infrared spectroscopy and chemical analysis. Poly(carbonsuboxide) was obtained by polymerization of carbonsuboxide C3O2, which in turn was synthesized from malonic acid bis(trimethylsilylester). Two different 13C labeling schemes were applied to probe inter- and intramonomeric bonds in the polymer by dipolar solid-state NMR methods and also to allow quantitative 13C MAS NMR spectra. Four types of carbon environments can be distinguished in the NMR spectra. Double-quantum and triple-quantum 2D correlation experiments were used to assign the observed peaks using the through-space and through-bond dipolar coupling. In order to obtain distance constraints for the intermonomeric bonds, double-quantum constant-time experiments were performed. In these experiments an additional filter step was applied to suppress contributions from not directly bonded 13C,13C spin pairs. The 13C NMR intensities, chemical shifts, connectivities and distances gave constraints for both the polymerization mechanism and the short-range order of the polymer. The experimental results were complemented by bond lengths predicted by density functional theory methods for several previously suggested models. Based on the presented evidence we can unambiguously exclude models based on gamma-pyronic units and support models based on alpha-pyronic units. The possibility of planar ladder- and bracelet-like alpha-pyronic structures is discussed.

show abstract

“…Die Spindichte erreicht 10 19 g À1 , obwohl die Polymerisation nicht über einen Radikalmechanismus verläuft. [9] Die Infrarotspektren zeigen, unabhängig von der Herstellungsweise, das gleiche Bandenmuster. Stellt man das Polymer unter strengstem Wasserausschluss her, zeigt das IRSpektrum eine Bande bei 2180 cm À1 , die der C = C = O-Gruppe zugeordnet wird.…”

unclassified

Analyse von polymerem Kohlensuboxid durch Röntgenkleinwinkelstreuung

Ballauff

Rosenfeldt

et al. 2004

Angewandte Chemie

View full text Add to dashboard Cite

Kohlenstoff bildet mehrere Oxide, von denen Kohlenmonoxid und Kohlendioxid zu den bestuntersuchten chemischen Verbindungen überhaupt gehören. Das stabilste Oxid mit mehr als zwei kumulierten Doppelbindungen ist das Kohlensuboxid (C 3 O 2 , 1; Schema 1), das vor fast 100 Jahren zum ersten Mal synthetisiert wurde: 1906 entdeckten Diels et al. bei der Dehydratisierung der Malonsäure mit P 4 O 10 ein farbloses, stechend riechendes Gas, das sie als C 3 O 2 identifizierten.[1] Das Molekül, dessen elektronische Struktur einen linearen Aufbau erwarten lässt, wurde intensiv spektroskopisch untersucht -das Ergebnis war eine quasilineare Struktur mit einer sehr kleinen Energiebarriere von etwa 30 cm À1 für die Knickschwingung am zentralen C-Atom. [2][3][4] Erst in jüngster Zeit gelang die Strukturaufklärung von kristallinem C 3 O 2 . [5] Eine besondere Eigenschaft von Kohlensuboxid ist seine spontane Polymerisation, die zu einem rot bis schwarz gefärbten Feststoff mit der unveränderten Zusammensetzung C 3 O 2 führt.[1] Der Aufbau des polymeren Kohlensuboxids (C 3 O 2 ) n war auf der atomaren Ebene allerdings bis heute nicht gesichert. Da das Polymer stets in amorpher Form anfällt, sind konventionelle Beugungsmethoden nicht anwendbar. Die Polymerisation ist exotherm (À136 kJ mol À1 ) und kann sogar explosionsartig ablaufen.[6] Sie verläuft nach einem Geschwindigkeitsgesetz 1. Ordnung und wird durch Spuren von Wasser, Säuren, Basen oder g-Strahlung katalysiert.[7] Ist kein Initiator vorhanden, hängt die Polymerisation von der Beschaffenheit der Gefäßoberfläche ab.[8] Das Polymer ist paramagnetisch, die Suszeptibilität folgt dem CurieWeiss-Gesetz. Die Spindichte erreicht 10 19 g À1 , obwohl die Polymerisation nicht über einen Radikalmechanismus verläuft.[9] Die Infrarotspektren zeigen, unabhängig von der Herstellungsweise, das gleiche Bandenmuster. Stellt man das Polymer unter strengstem Wasserausschluss her, zeigt das IRSpektrum eine Bande bei 2180 cm À1 , die der C = C = O-Gruppe zugeordnet wird. Diese Bande verschwindet zusammen mit dem paramagnetischen Moment schon nach kurzer Exposition an feuchter Luft. [7] Es gibt mehrere Vorschläge für die Struktur. Von diesen wurden die frühen Hypothesen eines Poly(spirocyclobutandions) [10] und eines ungeordneten, ebenen Moleküls, dessen Ränder mit C=O-und C=C=O-Gruppen besetzt sind, [11] wegen spektroskopischer Befunde verworfen.[12] Die 1960 von Ziegler [13] erstmals postulierte Poly-a-pyronstruktur (2; Schema 1) wurde wenig später durch andere Studien bekräf-tigt [8,12] und hat inzwischen Eingang in die Lehrbücher gefunden. Dieser Vorschlag wurde jedoch in jüngerer Zeit in Frage gestellt, da die Säure-Base-Titration des Polymers auf zwei unterschiedliche, schwach saure Gruppen hinweist. Dies wurde mit dem Vorhandensein von sowohl a-als auch gPyroneinheiten im Strang erklärt. [14] Die Diskussion um die Struktur von (C 3 O 2 ) n kann nicht als abgeschlossen gelten, da gerade der für das Verständnis der Polymerstruktur wichtige Polymerisationsgrad n noch nicht geklärt ist. Bei Temper...

show abstract

Poly(carbon suboxide): A photosensitive paramagnetic ladder polymer

Cited by 19 publications

References 33 publications

Metastable phases and ‘metastable’ phase diagrams

Metastable phases and ‘metastable’ phase diagrams

The Structure of Poly(carbonsuboxide) on the Atomic Scale: A Solid‐State NMR Study

Analyse von polymerem Kohlensuboxid durch Röntgenkleinwinkelstreuung

Contact Info

Product

Resources

About