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  • Articles  (435)
  • Polymer and Materials Science  (371)
  • Condensed Matter: Electronic Properties, etc.  (64)
  • 2015-2019  (64)
  • 1995-1999  (225)
  • 1980-1984  (105)
  • 1965-1969  (41)
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  • Articles  (435)
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  • 1
    Electronic Resource
    Electronic Resource
    Stereoselective polymerization of butadiene by a new dicationic nickel complex (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 33-41 
    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: Der neuartige dikationische Komplex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-Bis(diphenylphosphin)ferrocen) zeigte in Anwesenheit von Diethylaluminiumchlorid (AIEt2CI) hohe Aktivität für die Polymerisation von 1,3-Butadien. Reaktionsdauer, Temperatur und das Aluminium/Nickel-Verhältnis wurden auf maximale Aktivität und Selektivität optimiert. Umsätze über 90% konnten erreicht werden. Im Vergleich zu Polybutadienen, die mit anderen Nickel-Phosphin-Systemen hergestellt wurden, zeigten die synthetisierten Polybutadiene höhere cis-1,4-Anteile (〈80%) und eine geringe Bildung von 1,2-Einheiten (2%). Alle Polymeren hatten niedrige mittlere Molekulargewichte (Mw 〉 11 800).
    Notes: The new dicationic nickel complex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt2CI) exhibited high activity on the 1,3-butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel-based systems using phosphine ligands, the resulting polybutadiene showed high cis-1,4 (〈80%) content and only small amount of 1,2-units (2%). All polymers presented low molecular weights (Mw 〉 11 800).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052390104
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and properties of aromatic polyamides with oligobenzamide pendent groups. I. Poly-5-(4-benzoylamino-1-benzoylamino)isophthalamides (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1987-1994 
    Details
    ISSN: 0887-624X
    Keywords: aromatic polyamides ; polyisophthalalamides ; pendent oligomeric benzamide groups ; 5-(4-benzoylamino-1-benzoylamino)isophthalic acid ; water uptake ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of polyisophthalamides having pendent oligomeric benzamide groups were prepared by the Yamazaki reaction from common aromatic diamines and 5-(4-benzoylamino-1-benzoylamino)isophthalic acid. The latter was synthesized from 5-aminoisophthalic acid in a three-step synthesis by successive incorporation of benzamido groups. The new polymers were characterized by NMR, DSC, TGA, and WAXD and the properties were compared to those of corresponding unsubstituted polyisophthalamides. All of the polymers were essentially amorphous and their Tgs were about 20°C higher than the reference polymers. Initial thermal decomposition temperatures ranged from 375 to 420°C. All of the polymers were soluble in aprotic polar solvents without added salts. Properties of particular note were: the water uptake, which was particularly high, ranging from 7.5 to 18.2%, and the temporary insolubilization in concentrated sulfuric acid of films of the polymers heated for a short time to ≥ 200°C. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331205
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of the photoinitiated inverse microemulsion polymerization of 2-methacryloyl oxyethyl trimethyl ammonium chloride (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 737-748 
    Details
    ISSN: 0887-624X
    Keywords: inverse microemulsion polymerization ; MADQUAT ; nucleation ; photopolymerization ; molecular weights ; flocculants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of inverse microemulsions of 2-methacryloyl oxyethyl trimethyl ammonium chloride stabilized by a blend of nonionic emulsifiers (a sorbitan sesquioleate and a sorbitan monooleate) and initiated by UV light in the presence of Azobis(isobutyronitrile) (AIBN) was investigated. The effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the polymerization rate (Rp), number of polymer particles (Np), and polymer molecular weight (Mw) was studied. The application of this process to tubular reactors is discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 737-748, 1998
    Additional Material: 15 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Aliphatic-aromatic poly(ether amide)s containing oxyethylene units. Synthesis and characterization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 659-667 
    Details
    ISSN: 0887-624X
    Keywords: condensation monomers ; amide-ether copolymers ; solution and interfacial polycondensation ; NMR ; GPC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of aromatic polyamides containing oxyethylene units is reported, and the differences observed in polycondensation yields, molecular weights, and molecular weight distributions, as a function of the method of synthesis, are discussed. Four diamines containing oxyethylene units and aromatic rings, meta and para oriented, and their corresponding hydrochlorides were prepared as condensation monomers to be combined with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC). High molecular weight polyamides were obtained by interfacial and low-temperature solution methods. Values of (OVERLINE)M(/OVERLINE)n up to 6 × 104 g/mol and (OVERLINE)M(/OVERLINE)w up to 2 × 105 g/mol could be measured by gel permeation chromatography using aromatic polyamide standards, and values of (OVERLINE)M(/OVERLINE)n up to 2 × 105 g/mol and (OVERLINE)M(/OVERLINE)w up to 5 × 105 g/mol by using polystyrene standards. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of novel polyaryl(ether-ketones) with tert-butyl pendent groupsDedicated to Prof. F. J. Baltaá Calleja on the occasion of his 60th birthday. (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1251-1256 
    Details
    ISSN: 0887-624X
    Keywords: ether ketones ; synthesis ; NMR ; thermal properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether-ketones). The current polyaryl(ether-ketones) showed glass transition temperatures in the range 170-240°C and decomposition temperatures, as measured by TGA, of about 500°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1251-1256, 1998
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Dielectric relaxation processes in a brick-like metallomesogen ferroelectric liquid crystalThis work was supported by the Spanish Government (projects: CICYT Mat-94-0717-C02-02 and DGCYT PB91-0554) and the European Community (Human Capital and Mobility Programme ERB4050 Pl922749). Santos Merino thanks the Basque Government for provision of his grant. (1996)
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 644-647 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19960080808
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