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  • Wiley-Blackwell  (22)
  • PANGAEA
  • Springer Science + Business Media
  • 1995-1999  (24)
  • 1997  (24)
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Keywords
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  • 1995-1999  (24)
Year
  • 1
    Electronic Resource
    Electronic Resource
    A New Lithium 5-Methyl-1,3-dithia-5-azacyclohex-2-ylborate  - 5-Borane and Two Dimeric 5-Methyl-1,3-dithia-5-azacyclohex-2-yllithium Compounds  -  Stereochemistry and Reactivity (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 813-817 
    Details
    ISSN: 0009-2940
    Keywords: Lithium 5-Methyl-1,3-dithia-5-azacyclohex-2-ylborate - 5-borane ; 5-Methyl-1,3-dithia-5-azacyclohex-2-yllithium ; Nitrogen heterocycles ; Sulfur heterocycles ; Lithium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of the dimers of axial 5-methyl-2-dithiazinyllithium (4) and equatorial 5-methyl-2-diethiazinyllithium-5-borane (5), and lithium 5-methyl-2-dithiazinanylborate-5-borane (6) are reported. Compounds 4, 5, and 6 are configurationally and conformationally stable. The 1H-, 13H-, 13C-, 11B-, and 7Li-NMR study of th reactions of 4 and 5 with BH3—S(CH3)2, BH3 - THF, and CH3I is presented.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300622
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of poly(aryl ether) dendrimers using an aryl carbonate and mixtures of metal carbonates and metal hydroxides (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1781-1798 
    Details
    ISSN: 0887-624X
    Keywords: poly(aryl ether) dendrimers ; cascade polymers ; polyetherification reaction ; divergent approach ; activation/condensation sequence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four generations of poly(aryl ether) dendrimers containing aryl sulfide or aryl sulfone groups, and aryl fluoride terminal functionality, have been synthesized using the divergent initiator core method and bis(4-fluorophenyl) sulfone as the core precursor. The strategy is based on the divergent approach and an activation/condensation sequence that involves oxidation of the aryl sulfide group and the displacement of the activated halide moiety by a phenolate ion. The phenolate is easily generated in situ from an aryl carbonate. No reaction intermediates were detected when the condensation reaction was carried out utilizing a very active metal carbonate, such as cesium carbonate, in conjunction with magnesium hydroxide or calcium carbonate which removes some of the fluoride ions formed. The samples were characterized by HPLC, MALDI-TOF-MS, NMR, and SEC. Imperfections in some of the molecules of the dendrimers, formed by reaction of the core precusors with an impurity present in the phenol, were also identified by MALDI-TOF-MS. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1781-1798, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of hyperbranched macromolecules with aryl fluoride and phenol terminal functionalities using new monomers and Cs2CO3 or Mg(OH)2 as the condensation agent (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2015-2033 
    Details
    ISSN: 0887-624X
    Keywords: hyperbranched ; aryl ether sulfone ; polycondensation ; divergent approach ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New A2B monomers were synthesized for preparation of hyperbranched aryl ether sulfone macromolecules with aryl fluoride and phenol terminal functionalities. The macromolecules, which possess high thermal stability, were prepared using the divergent approach. A masked phenol with two aryl fluoride groups and a bisphenol with an aryl fluoride group were the monomers used to synthesize these polymers. In both cases, the aryl fluoride group is activated by a sulfone moiety. The synthetic method used for the preparation of the hyperbranched macromolecules gave a fast reaction and a high yield. These methods include, e.g., the use of Cs2CO3 and Mg(OH)2 to generate the phenolate ion in situ. Use of the latter results in the formation of insoluble magnesium fluoride. The best conditions for the reaction utilized the more active nucleophilic polycondensation agent, Cs2CO3, and an aryl carbonate as a masked phenol. NMR, SEC, and MALDI-TOF-MS were used to characterize the samples. MALDI-TOF-MS allowed us to identify the different oligomeric species present, and it also indicated that an internal cyclization competes with the polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2015-2033, 1997
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous drying of a solid wetted with ternary mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 681-692 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol-isopropanol-water and water-ethanol-acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430314
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  • 5
    Electronic Resource
    Electronic Resource
    Optimization of a process for the synthesis of a sperm whale oil analogue (1997)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 20 (1997), S. 287-292 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development and optimization of the synthesis of an analogue of sperm whale oil have been carried out. The product is an ester with characteristics similar to those of natural sperm whale oil. A central composite design was applied in the synthesis of this fine chemical. The variables selected for the present study are reaction temperature, initial concentration of catalyst and working pressure. Temperature is the most significant factor in the esterification process, and its influence is positive. Pressure influence can be neglected, and the catalyst concentration has a positive influence on the process. Depending on the temperature value, the influence of the interactions can be more important than that of the other two main effects, pressure and catalyst concentration. Response surface models have been found adequate to represent the yield of ester. The commercial quality of the synthesized product is very similar to that of natural spermaceti. Because of its low cost, this synthesis process is considered, from an economical point of view, very attractive.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270200411
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of surface fractality on the permeability of transparent gas barrier coatingsThis work was financially supported through BRITE EURAM II project BRE 2-CT92-0237 and the CSIC/CONICET cooperation program. The authors are indebted to CE.TE.V. (Italy) for providing the samples and performing the water vapor diffusivity measurements. They are also indebted to Otto Nielsen Emballage (Denmark) for performing the oxygen permeability measurements. (1997)
    Weinheim : Wiley-Blackwell
    Advanced Materials 9 (1997), S. 654-658 
    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: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19970090815
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  • 7
    Electronic Resource
    Electronic Resource
    Deformation, scattering, and birefringence of flexible polymer chains under external forces or electric fields (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 689-697 
    Details
    ISSN: 0887-6266
    Keywords: tensile force ; electric field ; chain conformation ; birefringence ; scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of a tensile stress or an electric field on the conformation of a flexible polymer chain has been studied by combining theory with numerical simulation. In the presence of such external agents, the macromolecule experiences the action of two opposite forces at the chain ends. Two models are considered: the Gaussian bead-and-spring chain, and the freely jointed chain with segments of fixed length. From simulated Brownian trajectories we calculate steady-state properties of the polymer under the continuing action of the external forces. Thus, we compute the chain deformation and expansion, measured by the square radius of gyration, and analyze the influence of the external force on low-angle scattering of radiation. The effect of the link orientation in the optical anisotropy or birefringence is also analyzed. From existing theories, we predict very simple relationships between expansion, low-angle scattering, and birefringence, valid for Gaussian chains of any length, and for long freely jointed chains. The simulation results confirm those relationships. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 689-697, 1997
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Polymorphism in an oligo(aryl ether ketone)Dedicated to Prof. Dr. F. J. Baltá Calleja on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2089-2099 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1,3-Bis(4-phenoxybenzoyl)benzene (1) shows a single melting peak at T1 = 120°C when rapidly crystallized from a methanol/benzene mixture (10:1 v/v) (sample A) and a double melting peak at T1 = 120°C and T2 = 130°C when crystallized slowly (overnight) (sample B). Slow recrystallization of 1 using ethanol instead of methanol induces the formation of large single crystals which only show a single melting peak at T2 = 130°C (sample C). Analysis of powder X-ray diffractograms obtained for A, B and C samples clearly point out the coexistence of two crystalline phases in sample B: phase 1 (observed for sample A) and phase 2 (sample C). From optical microscopy and thermal (DSC) observations, it can be concluded that, upon heating, phase 1 melts at T1 and the molten material converts itself into phase 2 if some crystals of phase 2 are present. Single crystal structure determination of, both, phase 1 and 2 reveal conformational differences of the molecule in both phases which pack in an orthorhombic and a monoclinic unit cell, respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980707
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of polymeric organic-inorganic hybrid materials. Partially deacetylated chitin-silica hybrid (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 163-167 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work reports the synthesis of a novel polymeric organic-inorganic hybrid. The inorganic component is a silica network obtained by controlled hydrolysis of tetraethyl orthosilicate via sol-gel process and the organic counterpart is partially deacetylated chitin (CHI). The resulting polymer hybrids were homogeneous transparent film forming glassy materials being compatible through a wide composition range. Simultaneous thermal analysis of a CHI/silica 1:1 mixture confirms the intermolecular complex formation between organic and inorganic polymers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180214
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  • 10
    Electronic Resource
    Electronic Resource
    Branched poly(ethylene glycol) linkers (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2489-2498 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel types of methoxy poly(ethylene glycol) (PEG) linkers (U-PEG linkers) have been synthesized. These PEG linkers are linear polymers that attach to bioactive agents via a functional group, derived from a 2° alcohol, located in the center of the polymer chain versus the traditional terminal attachment site. These new types of linkers can be prepared with different functional groups (e.g. active ester, succinimidyl carbonate, and carbazate) for selected point of attachment, including ethylene oxide oligomers to provide “stems” when steric factors need to be addressed. Conversion of p-nitrophenyl carbonates to the more desirable succinimidyl carbonates has also been accomplished by a novel nucleophilic displacement procedure. Modification of proteins with these reagents is easily accomplished and is illustrated by the conjugation of a U-PEG linker with L-asparaginase.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980810
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