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  • 1
    Electronic Resource
    Electronic Resource
    Conformational analysis of 1,1,2,2-tetracyclohexylethane (1979)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 101 (1979), S. 4493-4497 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00510a010
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  • 2
    Electronic Resource
    Electronic Resource
    Thermolabile Kohlenwasserstoffe, XVI. Thermische Stabilität, Spannungsenthalpie und Struktur symmetrisch tetrasubstituierter Ethane (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 3364-3383 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XVI. Thermal Stability, Strain Enthalpy, and Structure of Sym. Tetrasubstituted EthanesActivation parameters were determined for the thermolysis reaction of 12 sym. tetrasubstituted ethanes (Ct—Ct series). From product analyses it was concluded that the central Ct—Ct bond is cleaved in the rate determining step by homolysis. The correlation between ΔH≠ and the change in strain enthalpy during the activation process (MM2 calculations) points to nearly 20% residual strain at transition state. From a comparison of the thermolysis data for Ct—Ct and Cq—Cq ethanes a 2.3 kcal · mol-1 difference in stabilization energy for sek. and tert. alkyl radicals is derived as an upper limiting value. The influence of strain on bond lengths, bond angles, and torsional angles is compared for Ct—Ct and Cq—Cq ethanes.
    Notes: Die Aktivierungsparameter der Thermolyse von 12 symmetrisch tetrasubstituierten Ethanen (Ct—Ct-Reihe) wurden bestimmt. Produktanalysen belegen, daß im Primärschritt der Thermolyse die zentrale Ct—Ct-Bindung homolytisch gespalten wird. Aus der Korrelation zwischen ΔH≠ und der Abnahme der Spannungsenthalpie im Zuge der Bindungsdissoziation (Kraftfeldrechnungen) folgt, daß im Übergangszustand der Thermolyse noch ungefähr 20% Restspannung verbleiben. Aus dem Vergleich der Thermolyse von Ct—Ct- und Cq—Cq-Ethanen läßt sich 2.3 kcal ·mol-1 als oberer, vermutlich zu hoher Grenzwert für den Unterschied der Stabilisierungsenergie sek. und tert. Alkylradikale angeben. Der Einfluß der Spannung auf Bindungslängen, Bindungs- und Torsionswinkel wird mit den Verhältnissen in der Cq—Cq-Ethanreihe verglichen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821151014
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  • 3
    Electronic Resource
    Electronic Resource
    Thermolabile Kohlenwasserstoffe, IV: Tetra-tert-butylethan (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 72-83 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, IV: Tetra-tert-butylethaneDue to steric acceleration of bond homolysis tetra-tert-butylethane (3,4-di-tert-butyl-2,2,5,5-tetramethylhexane, 1) decomposes at 141°C with t1/2 = 1 h (ΔH≠ = 36.4 ± 0.5 kcal/mol; ΔS≠ = 11.8 ± 1.2 e.u.) into di-tert-butylmethyl radicals. Accordingly 1 is the most thermolabile alkane hydrocarbon known at present. From the kinetics and from thermochemical data as well as from molecular force field calculations a strain energy of ca. 63 kcal/mol is estimated. In agreement with the NMR spectra(3) the force field calculations result in a gauche conformation as structure of minimal energy for 1. Accordingly the central C—C-bond is elongated to ca. 1.60 Å, the bond CtCtH is compressed to ca. 97° and the torsional angle HCtCtH is ca. 101°.
    Notes: Infolge sterischer Beschleunigung zerfällt Tetra-tert-butylethan (3,4-Di-tert-butyl-2,2,5,5-tetra-methylhexan, 1) schon bei 141°C homolytisch mit t1/2 = 1 h(ΔH≠ =36.4 ± 0.5 kcal/mol; ΔS≠ = 11.8 ± 1.2 cal/mol·grad) in Di-tert-butylmethyl-Radikale. 1 ist der thermolabilste zur Zeit bekannte Alkankohlenwasserstoff. Die Spannungsenergie für 1 wurde aus kinetischen und thermochemischen Daten sowie Kraftfeldberechnungen zu ca. 63 kcal/mol abgeleitet. Die Kraftfeldberechnungen ergeben in Übereinstimmung mit NMR-Spektren(3) gauche-Konformation für 1 als Energieminimum. Die Bindungslänge der zentralen C—C-Bindung errechnet sich zu ca. 1.60Å, der Bindungswinkel CtCtH zu ca. 97° und der Torsionswinkel HCtCtH zu 101°.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110107
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  • 4
    Electronic Resource
    Electronic Resource
    The glass transition temperatures of homogeneous blends of polystyrene, poly(methyl methacrylate), and copolymers of styrene and methyl methacrylateDedicated to Prof. Dr. H.-J. Cantow on the occasion of his 65th birthday (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 1671-1679 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition temperatures Tg of homogeneous binary blends of the homo- and the statistical copolymers of the system poly(styrene-co-methyl methacrylate) were studied. Some of the blends, which are in the equilibrium phase separated, were forced into homogeneity. Tg (φ) of the homopolymer blends (PS/PMMA)φ follows the Fox equation, while Tg (x) of the pure copolymers P(SxMMA1 - x) exhibits a minimum. This minimum can be effectively removed by blending the copolymers with small fractions (φ ≈ 0,2) of one of the two homopolymers or a differently composed copolymer P(SyMMA1 - y).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890721
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  • 5
    Electronic Resource
    Electronic Resource
    Compatibility of tetramethyl polycarbonate and random poly(styrene-co-methyl methacrylate)s (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2749-2766 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phase diagrams and concentration fluctations of blends of tetramethyl polycarbonate (TMPC)Polycarbonate of 2,2′,6,6′-tetramethyl-4,4′-isopropylidenediphenol (tetramethyl derivative of bisphenol A). and random copolymers P(SxMMA1-x) of styrene and methyl methacrylate were analyzed, using cast films and dry films. Phase separation was detected by light microscopy, DSC and small-angle neutron scattering. Neutron scattering was also used to measure the structure of fluctuations in one-phase as well as two-phase states. The merits and problems of the various methods are discussed. Blends TMPC/P(SxMMA1-x) have high-temperature miscibility gaps at x 〉 0,5. The copolymers interact non-ideally, in a manner that had been observed before in their blends with PS and PMMA. An equation based on the classical theory but allowing diad effects describes the interaction parameters fairly well. It was used to calculate the interaction parameter of the immiscible homopolymer blend TMPC/PMMA which was also determined from the miscibility gap of a ternary blend TMPC/PMMA/P(SxMMA1-x).
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021921120
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  • 6
    Electronic Resource
    Electronic Resource
    Polymerizable amphiphiles, 2. Micellization of 1-O-3-(4-vinylphenyl)propyl-β-D-glucopyranosePart 1: Cf.10. (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 537-560 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1-O-3-(4-Vinylphenyl)propyl-β-D-glucopyranose (1) undergoes in water a closed association under formation of N-mers. The unimer/N-mer association is directly visible in the Schlieren pattern of ultracentrifugal synthetic boundary experiments. Association numbers and mass-concentration-based equilibrium constants of association were calculated from the variation of N-mer concentrations with unimer concentrations and from the concentration dependence of inverse apparent average molar masses as measured by both vapor phase osmometry and sedimentation equilibrium. Association numbers were also calculated from the combination of sedimentation coefficients with diffusion coefficients, sedimentation coefficients with intrinsic viscosities, and diffusion coefficients with interinsic viscosities as well as from the dependence of apparent mass-average molar masses on inverse apparent number-average molar masses. All methods gave in general different association numbers and equilibrium constants. The effect, which was not found for other non-ionic amphiphiles, is probably due to the existence of consecutive equilibria between the unimer and a low molar mass P-mer which associates to a higher molar mass R-mer. Viscosity data are in agreement with the picture of a spherical micelle for the dominant P-mers with about 10 water molecules per glucose residue. The micellization of 1 is both enthalpy- and entropy-driven, in contrast to the micellization of 1-O-octyl-β-D-glucopyranose which is a strictly entropy-driven process.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880308
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  • 7
    Electronic Resource
    Electronic Resource
    Blend phase diagrams recorded with cast films (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2615-2633 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phase diagrams of amorphous polymer blends are discussed that are recorded using cast films. Films of all blend compositions were cast at temperatures ranging over a wide interval, using different solvents, both above and below the glass transition temperatures of the blends. Phase diagrams thereby obtained can, if there is a proper choice of solvents and conditions, show the miscibility of polymers not only in the liquid but also in the glassy state. The theory of blend film casting is analyzed using the classical Flory-Huggins model for compatibility and the Fox-equation for the glass transition. It turns out that miscibility is reliably determined when slightly selective solvents are used. Errors made with non-selective and too selective solvents are estimated. The film-casting method was tested with blends of poly(methyl methacrylate) and random copolymers of styrene and methyl methacrylate.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021921108
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  • 8
    Electronic Resource
    Electronic Resource
    Nachweis einer linearen Beziehung zwischen thermischer Stabilität und Spannungsenergie von AlkanenThermolabile Kohlenwasserstoffe, 5. Mitteilung. Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft, dem Fonds der Chemischen Industrie und der Otto-Röhm-Gedächtnisstiftung unterstützt. 4. Mitteilung: H.-D. Beckhaus, G. Hellmann, C. Rüchardt Chem. Ber., im Druck. (1977)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 89 (1977), S. 913-914 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19770891228
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  • 9
    Electronic Resource
    Electronic Resource
    Rigid-chain polyesters grafted with flexible-chain vinyl polymers (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 73-88 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In den letzten zehn Jahren wurde, als Alternative zur Faserverstärkung von Thermoplasten, das Konzept der “molekularen Faserverstärkung” vorgeschlagen: Die starren Ketten von Hauptketten-LC-Polymeren (PLC) können in Blends mit normalen Thermoplasten (d.h. mit beweglichen Ketten) als Fasern molekularer Größe fungieren. Steifkettige und normale Thermoplaste sind aber in der Regel zu unverträglich, um die für diesen Mechanismus notwendige molekulare Verteilung der starren Ketten zu erlauben. In diesem Bericht wird als verwandtes Konzept die “mizellare Faserverstärkung” diskutiert: Pfropfcopolymere aus einem starren PLC-Rückgrat und flexiblen Pfropfästen können Mikrophasenmorphologien mit zylindrischen Mizellen aufbauen, in denen die PLC-Ketten als verstärkende Fasern mit mizellaren Dimensionen fungieren. Starr-bewegliche Pfropfcopolymere dieser Art wurden aus einem Polyester mit Terephthaloyl-, Dihexoxyterephthaloyl- und Phenylhydrochinoneinheiten sowie aus Polystyrol hergestellt. Die Polyesterketten wurden mit Spezialcomonomeren mit einer Doppelbindung modifiziert, auf die im Zuge einer radi-kalischen Copolymerisation Polystyroläste gepfropft wurden. Hohe Pfropfgrade führten zu Produkten mit der erwünschten Morphologie von zylindrischen Mizzellen.
    Notes: The concept of “molecular reinforcement” has been advanced, in the last decade, as an alternative to conventional fibre reinforcement of thermoplastics: In blends with normal (flexible-chain) thermoplastics, rigid chains of main-chain LC polymers (PLC) can act as strengthening fibres on the molecular scale. However, the rigid PLC chains must be well dispersed which is improbable since PLC and normal polymers are usually incompatible. A related concept is “micellar reinforcement”: Graft copolymers made of a rigid-chain PLC backbone and flexible-chain grafts can form a microphase morphology of cylinderic micelles where the PLC chains act as reinforcing fibres on a micellar scale. Such rigid-flexible graft copolymers are discussed in this study. They were pepared from a polyester of terephthaloyl, dihexoxyterephthaloyl and phenylhydroquinone moieties with special comonomer units carrying a double bond onto which styrene was grafted via radical copolymerisation. Grafting occurred with high efficiency, leading to products with the desired morphology of cyclindric micelles.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450107
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  • 10
    Electronic Resource
    Electronic Resource
    Heterogeneous grafting of maleic anhydride and α-methylstyrene from atactic polypropylene (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 37-48 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ataktisches Polypropylen (PP) ist ein amorphes, kurzkettiges Nebenprodukt des isotaktischen Polypropylens (iPP). Wegen seiner erhöhten Löslichkeit ist PP ein günstiges Modellpolymeres für Studien der Kinetik von iPP-Schmelzereaktionen. Untersucht wurde die Maleinierung von PP durch radikalische Pfropfung in der Schmelze. Da Maleinsäureanhydrid (MAA) verfärbende Oligomere bildet, wurde PP mit einer Mischung aus MAA und α-Methylstyrol (MS) gepfropft. Von Vorteil ist, daß MS bei hohen Temperaturen nicht homopolymerisieren kann und daß MAA und MS praktisch alternierende, farblose Copolymere liefern. Die Kinetik des Pfropfprozesses kompliziert sich durch eine Phasenseparation von PP und [MAA+MS], die bei höheren Monomerkonzentrationen auftritt und von speziellen Wechselwirkungen zwischen den beiden Monomeren ausgelöst wird. Deswegen werden zwei gepfropfte PP-Produkte gebildet, ein wenig gepfropftes Hauptprodukt und ein hochgepfropftes Nebenprodukt. Dieses entsteht vermutlich in den Phasengrenzflächen. Es trägt pro PP-Kette einen MAAMS-Ast, der ungefähr aus drei MAA- und fünf MS-Bausteinen besteht.
    Notes: Atactic polypropylene (PP) is an amorphous short-chained by-product of isotactic polypropylene (iPP). Due to its enhanced solubility, PP is a suited model polymer for kinetic studies of iPP melt reactions. The maleination of PP via radical grafting at high temperatures was investigated. Since maleic anhydride (MAA) produces discoloring oligomers, PP was grafted with a mixture of MAA and α-methylstyrene (MS). Advantageous is that MS cannot homopolymerize at high temperatures and that MAA and MS tend to copolymerize alternatingly (to colorless products). The kinetics of the grafting process is complicated by a phase separation of PP and [MAA+MS] that is caused by the special attractions between the two monomers. As a result, two grafted PP products are obtained, of which the major is only slightly but the minor is heavily grafted. The latter graft copolymer, which is probably created in the interfaces between phase domains, carries one MAAMS graft per PP back bone chain, approximately with three MAA and five MS units.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052510104
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