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  • Polymer and Materials Science  (300)
  • Physics  (57)
  • 1980-1984  (105)
  • 1975-1979  (92)
  • 1970-1974  (62)
  • 1965-1969  (41)
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  • 1
    Electronic Resource
    Electronic Resource
    The radical initiation of vinyl polymerization by α.α.α′.α′-Tetrasubstituted dibenzyls (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 157 (1972), S. 279-298 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Im Temperaturbereich von 60 bis 100°C wird die radikalische Polymerisation von Styrol, Methylmethacrylat und Acrylnitril von α.α′-Dicyanodibenzylen ausgelöst, die in α-und α′-Stellung mit Ester-, Nitril-, Amid- oder Phenylgruppen disubstituiert sind. Bei 100 bis 110°C ist auch das α.α.α′.α′-Tetracarboxymethyldibenzyl aktiv. Vinylacetat und Vinylchlorid werden durch diese Initiatoren kaum polymerisiert.Fur die Polymerisation des Styrols wurden die Bruttogeschwindigkeitskonstanten Kp, für viele Dibenzyle und fur Peroxide vergleichbarer Aktivitat dilatornetrisch bestirnrnt. Norrnalerweise sind die Zeit-Urnsatz-Kurven rnit den Dibenzylen und den Peroxiden vergleichbar; das Tetracyanodibenzyl allerdings bewirkt nur eine unvollstandige Polymerisation.Der große Einfiuß von Substituenten in α-Stellung oder in den Phenylringen der Dibenzyle auf die Polymerisation des Styrols wird diskutiert. Dabei ist auch die Stereochernie wichtig. Die meso-Form des Dinitrildiesters ergibt eine 2.5- bis 3.5 ma1 schnellere Polyrnerisation als das dl-Isornere.Die Dissoziationsgeschwindigkeitskonstanten kd der Initiatoren wurden NMR-spektroskopisch aus der Linienbreite bestirnmt. Die Dinitrildiester sind gute Initiatoren, wahrend die α.α′-Dicyanodibenzyle rnit weiteren Nitril- oder Phenylgruppen in α- und α′-Stellung wenig geeignet sind. SchlieBlich wurde die 1.2-Addition einiger der Dibenzyle an Styrol im Ternperaturbereich von 120 bis 150°C rnit der Methode der chernisch induzierten KernPolarisation (CIDNP) untersucht.
    Notes: The radical polymerization of styrene, methyl methacrylate and acrylonitrile is initiated by α.α′-dicyanodibenzyls α.α′-disubstituted with ester, nitrile, amide or phenyl groups in the temperature range 60 to 100°C and by α.α.α′.α′-tetracarboxymethyldibenzyl at 100 to 110°C. Vinylacetate and vinylchloride show a low reactivity.The overall polymerization rate constants Kp have been determined dilatometrically for styrene initiated by a large number of dibenzyls and comparable peroxides. The styrene polymerization curves are generally comparable with those of peroxides. A notable exception is tetracyanodibenzyl.The strong influence of α- and ring-substituents in the dibenzyls on the styrene polymerization rate is discussed. The stereochemistry is also important : the meso α.α′-dicyanodibenzyls α.α′-disubstituted with ester groups give a 2.5 to 3.5 fold faster polymerization than their dl isomers.The initiator efficiency is related to the kd values, determined from NMR line width measurements. The α.α′- dicyanodibenzyls α.α′-disubstituted with ester groups are good initiators, while those with phenyl groups and nitrile groups are inefficient.Relevant to initiation and termination, the 1.2-addition of some of the dimers to styrene at 120 to 150°C has been studied with chemically induced dynamic nuclear polarization (CIDNP).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021570128
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  • 2
    Electronic Resource
    Electronic Resource
    New structures of LD-alternating polypeptides in solution and in the solid state (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1109-1114 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140518
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between proton-proton nmr coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 1211-1245 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relationship between published vicinal proton-proton coupling constants and the pseudorotation properties of the pyrrolidine ring in L-proline, 4-hydroxy-L-proline, 4-fluoro-L-proline, and several linear and cyclic model proline peptides is investigated. Compared to earlier studies, several important improvements are incorporated: (1) a new empirical generalization of the classical Karplus equation is utilized, which allows a valid correction for the effects of electronegativity and orientation of substitutents on 3JHH; (2) an empirical correlation between proton-proton torsion angles and the pseudorotational parameters P and τm is derived; and (3) the best fit of the conformational parameters to the experimental coupling constants is obtained by means of a computerized iterative least-squares procedure. Two pseudorotation ranges were considered, classified as type N (χ2 positive sign) and type S (χ2 negative sign). The conformational equilibrium is fully described in terms of four geometrical parameters (PN, τN, PS, τS) and the equilibrium constant K. The present results indicate that, in general, the geometrical properties found in x-ray studies of proline and hydroxyproline residues are well preserved in solution. Several novel features are encountered, however. It is demonstrated that the proline ring occurs in a practically 1:1 conformational equilibrium between well-defined N- and S-type forms. Introduction of an amide group at the C-terminal end has no observable effect on this equilibrium, but the formation of a peptide bond at the imino nitrogen site results in a pronounced, but not exclusive, preference for an S-type form which is roughly 1.1 kcal/mol more stable than its N-type counterpart. The hydroxyproline ring system in neutral or acidic medium displays a pure N-type state, but N-acetylation results in the appearance of a minor (S-type) conformation. Cyclic proline dipeptides similarly exist in a biased conformational equilibrium. The major form (77-88%) corresponds to the N-type conformer observed in the solid state; the minor S-form has not been observed before. In contrast, cyclic hydroxyproline dipeptides display complete conformational purity. Ranges of endocyclic torsion angles deduced for the various classes of pyrrolidine derivatives in solution are presented. Each torsion appears confined to a surprisingly narrow range, comprising about 4°-8° in most cases. In all, the proline ring is far less “floppy” than hitherto assumed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200610
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  • 4
    Electronic Resource
    Electronic Resource
    Aliphatic-aromatic polyamide-imides from diisocyanates, 1. 1H and 13C NMR study of polymer structure (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 557-569 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of a diisocyanate and an asymmetric aliphatic-aromatic diacid containing a preformed imide group was studied in order to obtain polyamide-imides. It is shown in this paper that combined 1H and 13C NMR spectrometry will permit the quantitative evaluation of the proportions of head-tail, head-head, tail-tail additions, provided the content of urea in the polymer is low. In order to obtain unequivocal assignments and to thoroughly characterize the NMR spectra of the polymer, several model compounds resembling the polymer backbone were synthesized. A model polymer was synthesized with the same purpose, and its 1H and 13C NMR spectra fully assigned. Unexpected chemical functions in the polymer, like urea and carboxylic acid, can also be easily detected and quantified by NMR.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830305
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  • 5
    Electronic Resource
    Electronic Resource
    Aliphatic-aromatic polyamide-imides from diisocyanates, 2Part 1: cf.2.. Study of the influence of the reaction conditions on polymer structure (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 571-578 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polycondensation of 4,4′-methylenediphenylisocyanate and 6-(4-carboxyphthalimido)-hexanoic acid was studied under different conditions in order to establish the influence of factors such as temperature, catalyst, stoichiometric disbalance, and addition order of reactants on the molecular weight and the chemical composition of the final polyamide-imide. All these factors proved to influence the extent of possible side reactions that lead to undersirable functions, the main ones being urea functions that locate within the polymer backbone. Other side-reactions proposed to explain the formation of acylureas or biurets did not take place in appreciable extent since these functions could not be detected by NMR spectroscopy. Therefore, particular emphasis was made to prevent the formation of urea by changing the polycondensation conditions. A first attempt to clarify the regularity degree of the polymers (amounts of head to tail and head to head addition) by 1H NMR spectroscopy was also made.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830306
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and viscosity behavior of poly(γ-p-biphenylmethyl-L-glutamate) in benzene/dichloroacetic acid mixtures, a comparison with poly(γ-benzyl-L-glutamate) (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 3193-3206 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Darstellung von Poly(γ-p-biphenylmethyl-L-Glutamat), PBPLG, (Poly{L-imino-1-[2-(4-biphenylmethoxycarbonyl)äthyl]-2-oxoäthylen}), (1d) wird beschrieben. Das Viskositätsverhalten dieses Polymers in Mischungen aus Benzol und Dichloressigsäure (c=0,2.10 - 3 - 1,4.10 - 3g/cm3) bei 25°CC wird untersucht. Die Ergebnisse werden verglichen mit Messungen unter den gleichen Bedingungen an Poly(γ-benzyl-L-Glutamat),PBLG, (Poly[ L-imino-l-(2-benzyloxycarbonylathyl)-2-oxoathylen]), (lc). In beiden Fallenfindet ein zweistufiger Ubergang von einer starren, von Wasserstoffbrucken stabilisiertenHelix in ein statistisches, solvatisiertes Knduel statt : PBPLG (erste Stufe CrSSX,, zweite Stufe 55-100%, Dichloressigsaure und PBLG (erste Stufe 0-70%, zweite Stufe 70-100%,Dichloressigsaure)).Die Einfiihrung eines p-Phenylsubstituenten in PBLG fuhrt deshalb in Mischungen aus Benzol- und Dichloressigsaure zu einer weniger stabilisierten Helix.Die Stabilitat und das Viskositatsverhalten von PBLG in Mischungen aus Benzol und Dichloressigsaure (c=0,2.10-3 -14.10-3g/cm3) sind denjenigen von PBLG in Mi-schungen aus m-Kresol und Dichloressigslure ( c = 1,0.10-3-4,0. 10-3g/cm3) ähnlich.
    Notes: The synthesis of poly(γ-p-biphenylmethyl-L-glutamate), PBPLG, (poly{L-imino-1-[2-(4-biphenylylmethoxycarbonyl)ethyl]-2-oxoethylene}), (1d) is described. The viscosity behavior of this polymer in benzene/dichloroacetic acid mixtures (c=0,2.10 - 3 - 1,4.10 - 3 g/cm3) at 25°CC is investigated. The results are compared with measurements on poly(γ-benzyl-L-glutamate), PBLG, (poly[L-imino-1-(2-benzyloxycarbonylethyl)-2-oxoethylene]), (1c) under the same conditions. A transition from a rigid hydrogen bonded helix to a random solvated coil occurs in two stages for both: PBPLG (first stage 0 - 55%, second stage 55 - 100% dichloroacetic acid) and PBLG (first stage 0 - 70%, second stage 70 - 100% dichloroacetic acid).Therefore, the introduction of a p-phenyl substituent in PBLG leads to a less stable helix in benzene/dichloroacetic acid mixtures.The stability and viscosity behavior of PBLG in benzene/dichloroacetic acid mixtures (c=0,2.10 - 3 - 1,4.10 - 3g/cm3) is quite similar to the behavior of PBLG in m-cresol/dichloroacetic acid mixtures (c=1,0.10 - 3 - 4,0.10 - 3 g/cm3).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021751113
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  • 7
    Electronic Resource
    Electronic Resource
    Glass transition temperatures of copolymers (ethylene glycol/diethylene glycol) terephthalates (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3163-3168 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers of (ethylene glycol/diethylene glycol) terephthalates were prepared by melt polycondensation. The values of the glass transition temperatures of the copolyesters, determined by dilatometry are in fair agreement with those predicted by the Fox equation. It was also found that the conformational entropy can be used to correlate equilibrium flexibility and glass transition behaviour of the copolyesters.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021821122
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  • 8
    Electronic Resource
    Electronic Resource
    Poly(γ-p-nitrobenzyl-L-glulainate): synthetic aspects, sedimentation, and viscosity studies (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2509-2523 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of poly(γ-p-nitrobenzyl-L-glutamates), PNBG, has been synthesized by the polymerization of N-carboxyanhydride (NCA) derivatives of γ-p-nitrobenzyl-L-glutamate, NBG, using triethylamine as an initiator. We studied the influence of (a) the solvents dioxane, nitrobenzene, dimethylformamide (DMF), and DMF-1,2-dichloroethane mixture and (b) the anhydride-initiator ratio (A/I) for the polymerization in nitrobenzene (A/I varying from 50 to 750) on the properties of the polymers obtained. In order to improve its synthesis, NBG, was prepared by three different methods. Ten samples of PNBG, ranging in Mw from 10,000 to 50,000, were examined viscometrically in DMF and dichloroacetic acid (DCA) and by ultracentrifugation in DMF. The data for [η] and So (limiting sedimentation coefficient) as functions of Mw for PNBG in DMF were utilized, applying theories of Kuhn and Kuhn,13 Schachman,14 and Perrin, 15 for the estimation of the length per monomeric residue h. Viscosity data gave a h value of about 2.3 Å, Whereas sedimentation yielded 1.5 Å. Treating viscosity and sedimentation data for poly(γ-benzyl-L-glutamate), PBLG, in the same way leads to somewhat higher hvalues (2.4 Å and 1.7 Å, respectively).Although a nitroaromatic effect was shown to be absent for PNBG in DMF, it can be concluded that in this medium PNBG has a somewhat more compact structure than PBLG.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360101212
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  • 9
    Electronic Resource
    Electronic Resource
    Modern methods for the analysis of urea formaldehyde resins (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 54 (1976), S. 187-201 
    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: Moderne instrumentelle Methoden wurden zur Analyse von Harnstoff-Formaldehyd-Harzen verwendet. Ein ausführliches Studium der Silylierung des Harzes mittels BSTFA (N,O-Bistrimethylsilyltrifluoracetamid) ermöglicht die quantitative gaschromatographische Bestimmung der niedermolekularen Verbindungen Harnstoff, Monomethylolharnstoff und Dimethylolharnstoff. Das Verhältnis zwischen nieder- und hochmolekularen Verbindungen sowie die Mengen an niedermolekularen Verbindungen können mittels GPC-Analyse auf Sephadex LH 20 in Wasser ermittelt werden.Ein vollständiges Bild des Harzes erhält man durch 220 MHz 1H-NMR-Analyse von Lösungen von gefriergetrockneten Proben in DMSO-d6. Zusammen mit den Ergebnissen klassischer chemischer Analysen ergeben die Resultate der drei genannten Techniken einen guten Überblick über den Aufbau eines Harnstoff-Formaldehyd-Harzes.
    Notes: Modern instrumental techniques were used for analysing water-based urea-formaldehyde resins. An exhaustive study was made of the silylation of such a resin with BSTFA (N,O-bistrimethylsilyltrifluoroacetamide). From the gas chromatograms the amounts of urea, monomethylol urea and dimethylol urea can be determined quantitatively, thus giving information on the low molecular weight part of the resin. The ratio of low to high molecular weight components as well as the amounts of several low molecular weight compounds can be estimated from a GPC analysis on Sephadex LH 20 in water. A detailed picture of the resin is obtained when freeze-dried samples are subjected to 220 MHz 1H-NMR analysis in DMSO-d6.An overall insight into the composition of these resins can be gained when the results of the mentioned techniques are combined with those of classical chemical analyses.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1976.050540114
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  • 10
    Electronic Resource
    Electronic Resource
    13C-NMR analysis of formaldehyde resins (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 62 (1977), S. 7-31 
    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: Die 13C-NMR-Spektroskopie wurde zur Analyse von Formaldehyd-Harzen verwendet. Aus Phenolen, Harnstoff und Melamin wurden mit Formalin Harze hergestellt. Die chemischen Verschiebungen dieser Harze wurden relativ zu TMS gemessen. Alle Harze waren in DMSO-d6 löslich, so daß die Signale von unterschiedlichen Harzen verglichen werden konnten.Die Spektren wurden mit Hilfe der Spektren von Referenzsubstanzen und einfachen, auf Additivität basierenden Rechenregeln interpretiert. Jeder Harztyp hat sein eigenes spezifisches Spektrum und enthält Signale, die über die Struktur im Zusammenhang mit dem Katalysatortyp und der Kondensationsweise Auskunft erteilen. Die unterschiedlichen Formen, in denen Formaldehyd in diese Harze als Methylenkohlenstoff eingebaut ist, lassen sich unzweideutig aus dem Gebiet von 20 bis 100 ppm bestimmen.Diese Arbeit zeigt, daß sich die 13C-NMR Spektroskopie sehr gut für die Analyse von Formaldehydharzen eignet.
    Notes: 13C-NMR spectroscopy has been applied to the analysis of formaldehyde containing resins. Samples have been prepared from phenols, urea and melamine with formaldehyde. The chemical shifts of the carbon atoms in the resins were measured relative to TMS. All the samples could be dissolved in DMSO-d6 which facilitated the comparison of signals in different resins.The spectra were interpreted with the aid of spectra of reference compounds and simple calculations based on additivity increments. Each type of resin gives a specific 13C-NMR spectrum in which lines can be assigned that give information on the structure of the resin in relation to the type of condensation or catalyst used. Moreover, the different ways in which formaldehyde is incorporated in the resins as methylene carbon can be unambiguously determined from the region between 20 and 100 ppm.This work shows that 13C-NMR spectroscopy is a powerful tool for the analysis of formaldehyde containing resins.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1977.050620102
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