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  • Chemistry  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Transformation of the product set in separation sequence synthesis (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1753-1757 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690371123
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal Reaction of Highly Alkylated Azulenes with Dimethyl Acetylenedicarboxylate: HOMO(Azulene) vs. SHOMO(Azulene) Control in the Primary Thermal Addition Step (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 2447-2492 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of highly alkylated azulenes with dimethyl acetylenedicarboxylate (ADM) in decalin or tetralin at 180-200° yields, beside the expected heptalene- and azulene-1,2-dicarboxylates, tetracyclic compounds of type ‘anti’-V and tricyclic compounds of type E (cf. Schemes 2-4 and 8-11). The compounds of type ‘anti’-V represent Diels-Alder adducts of the primary tricyclic intermediates A with ADM. In some cases, the tricyclic compounds of type E also underwent a consecutive Diels-Alder reaction with ADM to yield the tetracyclic compounds of type ‘anti’- or ‘syn’-VI (cf. Schemes 2 and 8-11). The tricyclic compounds of type E, namely 4 and 8, reversibly rearrange via [1,5]-C shifts to isomeric tricyclic structures (cf. 18 and 19, respectively, in Scheme 6) already at temperatures 〉 50°. Photochemically 4 rearranges to a corresponding tetracyclic compound 20 via a di-π-methane reaction. The observed heptalene- and azulene-1,2-dicarboxylates as well as the tetracyclic compounds of type ‘anti’'-V are formed from the primary tricyclic intermediates A via rearrangement (→heptalenedicarboxylates), retro-Diels-Alder reaction (→ azulenedicarboxylates), and Diels-Alder reaction with ADM. The different reaction channels of A are dependent on the substituents. However, the main reaction channel of A is its retro-Diels-Alder reaction to the starting materials (azulene and ADM). The highly reversible Diels-Alder reaction of ADM to the five-membered ring of the azulenes is HOMO(azulene)/LUMO(ADM)-controlled, in contrast to the at 200° irreversible ADM addition to the seven-membered ring of the azulenes to yield the Diels-Alder products of type E. This competing reaction must occur on grounds of orbital-symmetry conservation under SHOMO(azulene)/LUMO(ADM) control (cf. Schemes 20-22). Several X-ray diffraction analyses of the products were performed (cf. Chapt. 4.1).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750803
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  • 3
    Electronic Resource
    Electronic Resource
    Interfacial phenomena controlling particle morphology of composite latexes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1049-1063 
    Details
    ISSN: 0021-8995
    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
    Notes: A thermodynamic analysis and a mathematical model were derived to describe the free energy changes corresponding to various possible morphologies in composite latex particles. Seeded batch emulsion polymerization was carried out at 70°C using as seed monodisperse polystyrene latex particles having different surface polarity. The surface polarity was estimated by contact angle measurement at the latex “film”/water interface for octane as the probe liquid. Methyl methacrylate and ethyl methacrylate were polymerized in a second stage seeded emulsion polymerization using polystyrene particles as seed in the presence of a nonionic stabilizer, nonyphenol polyethylene oxide (Igepal Co-990). Two types of initiators, potassium persulfate (K2S2O8) and azobisiobutyronitrile (AIBN), were used to change the interfacial tension between the second stage polymer (in monomer) and water interface. The values of the interfacial tension of polymer solutions in the second stage monomer vs. the aqueous phase, measured by drop-weight-volume method under conditions similar to those prevailing during the polymerization, correlated well with the determined particle surface polarity and the observed TEM particle morphology. The results showed that, rather than the polymer bulk hydrophilicity, the surface particle polarity is the controlling parameter in deciding which phase is inside or outside in the composite particle. The variation of the polymer phase interfacial tension with polymer concentration was also estimated. Based on experimentally measured interfacial tensions, composite particle configurations were predicted. The predicted morphologies showed good agreement with the observed particle morphologies of the composite latexes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420418
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  • 4
    Electronic Resource
    Electronic Resource
    Particle morphology in artificial composite polymer latex systems (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 691-706 
    Details
    ISSN: 0021-8995
    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
    Notes: Artificial composite latex particles were prepared by direct emulsification of a toluene solution of a blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The morphology of the composite particles from the higher molecular weight polymers showed polystyrene particles partially encapsulated by PMMA on the surface. On the other hand, for the lower molecular weight polymers, the reverse morphology was observed. The morphologies of the artificial composite latex particles swollen with solvent were examined when kept under agitation. The degree of phase separation between the two polymers in the composite particles was found to be affected by agitation to different extent, depending on the viscosity of polymer phases, the interfacial tension, and degree of mixing at interface between the two polymers. Extended agitation of the composite latex particles of high molecular weight polymers resulted in mixed morphologies that included individual PS and PMMA particles along with the original morphology of the composite particles. On the other hand, composite latex particles with the lower molecular weight polymers resisted complete phase separation due to lower interfacial tension and better mixing at the interface between the two polymers.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460416
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  • 5
    Electronic Resource
    Electronic Resource
    A general secular equation for cooperative binding of n-mer ligands to a one-dimensional lattice (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 1113-1121 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of n-mer ligands to a one-dimensional lattice involving many ligand species and complex multiple-binding mechanisms is studied. We show that, when derived using the sequence-generating function method of Lifson, the secular equation of any binding system with a finite number of “elementary units” can be expressed in a matrix determinant form that is very symmetric and easy to construct. In other words, for any binding system whose elementary units are known, the secular equation of the system can be obtained readily without going through the formal derivation of the equation. We also show that the “determinant” secular equation obtained using the present procedure can be employed directly to the calculation of binding isotherms.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360301111
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  • 6
    Electronic Resource
    Electronic Resource
    Theory of aggregation in solution. I. General equations and application to the stacking of bases, nucleosides, etc. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1285-1312 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Earlier theoretical work on aggregation in imperfect gases and in solutions of protein molecules is reformulated here in such a way as to be applicable to a number of aggregation systems in solution. The theory is most easily developed for an “osmotic” solution. It is exact, in principle, and in particular does not treat the aggregates as an ideal mixture as is usually done. If osmotic virial coefficients are diffcult to measure in a particular case, it is then necessary to relate these coefficients to properties of the more conventional “constant pressure” solution. An important special case is used as an example in the last three sections: The stacking of bases, nucleosides, etc., is represented by a statistical mecchanical model in which the aggregates resemble vertical stacks of checkers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120608
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  • 7
    Electronic Resource
    Electronic Resource
    Soapless emulsion polymerization of methyl methacrylate. II. Simulation of polymer particle formation (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 2235-2244 
    Details
    ISSN: 0021-8995
    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
    Notes: In this work, a generalized mathematical model was developed to estimate the variation of particle concentration during the entire course of soapless emulsion polymerization of methylmethacrylate (MMA). All of the factors, such as oligomeric radical absorption or desorption by polymer particles, coagulation between polymer particles, and the termination effect on the formation mechanism of polymer particles, were considered and included in this model. When appropriate parameters were selected, this model could be successfully used to interpret the experimental behavior of particle concentration during the entire reaction. Under different conditions, the rate of polymerization, the number of radicals in each particle, the instantaneous average molecular weight of polymers, and the rate constant of termination were also calculated. All of them coincided with the experimental results quite well. © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Degradation of medical-grade polyurethane elastomers: The effect of hydrogen peroxide in vitro (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 345-356 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Treatment of Pellethane 2363-80A - a medical-grade poly(tetramethylene oxide)-based polyurethane elastomer - with 25% (w/w) hydrogen peroxide at 100°C for times ranging from 24 h to 336 h led to significant decreases in ultimate tensile properties and decreases in molecular weight, both at the surface and in the bulk. IR spectral changes were similar to those observed after degradation in vivo. Differential scanning calorimetry showed that hydrogen-peroxideinduced degradation was associated with greater order in the hard domain and greater mobility in the soft domain. Studies conducted with low-molecular-weight model compounds for the hard and soft segments confirmed that methylene groups adjacent to oxygen were susceptible toward oxidation. The extent of degradation of a series of commercial polyurethanes on treatment with hydrogen peroxide (25%, 24 h, 100°C) correlated well with their reported susceptibility to environmental stress cracking in vivo. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820270308
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  • 9
    Electronic Resource
    Electronic Resource
    Enhancement of mechanical strength of poly(2-hydroxyethyl methacrylate) sponges (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 1029-1032 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290815
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of thionoesters on the degree of polymerization of styrene, methyl acrylate, methyl methacrylate and vinyl acetate (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 369-378 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aromatic thionoester 3 (benzyl thionobenzoate) was an effective chain transfer agent in polymerizations of styrene (Cx = 1,0) and methyl acrylate (Cx = 1,2) at 60°C. This activity was close to the ideal for obtaining narrow molecular-weight distributions in batch polymerizations. The thionoester 3 showed no activity in polymerizations of methyl methacrylate, but was too reactive to be useful in vinyl acetate polymerizations. Ring-substituted thionoesters 9-11 and 14 and 1H NMR spectroscopy of the resulting polymers were used to establish the type and quantity of end-groups. The thionoester 12 was used to produce low-molecular-weight polystyrene that was terminated at one end with a hydroxy group and at the other end by a thioloester moiety.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930209
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