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  • 1
    Electronic Resource
    Electronic Resource
    Activation and racemization of trifluoroacetate esters in the cationic polymerization of styrenePresented in part at the American Chemical Society Meeting, New Orleans, LA, September 1987. (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 3031-3042 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Phenylethyl trifluoroacetate (1) does not react directly with styrene but it is readily incorporated into polymer chains in the presence of an excess of trifluoroacetic acid. The proportion of the nondeuterated 1-phenylethyl end groups in the polymerization of deuterated styrene coinitiated with the acid was much higher than the proportion of the end groups formed by direct incorporation of the acidic protons ([CH3—CHPh—CD2—CDPh— …] 〉 [HCD2—CDPh—CH2—CDPh— …]). The racemization of the optically active ester-(pseudo-first order rate constant at [HA]0 = 0.79 mol/L at 20°C equals kR = 1.7 × 10-4 S-1) is more rapid than the incorporation of the ester into polymer chains (kE = 1.5 × 10-4 mol-1 Ls-1, [M]0 〈 0.4 mol L-1, i.e., kR 〉 kE · [M]). These results and the complete loss of the optical activity in the final polymer indicate that the ester is activated by the acid but it is incorporated into polymer chain via ionic intermediates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080261113
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  • 2
    Electronic Resource
    Electronic Resource
    Fibers from flexible liquid crystal main-chain polymers. I. Polymers based on 4,4′-dihydroxy-2,2′-dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 995-1007 
    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: The anisotropic properties of thermotropic liquid crystalline polymers are paramount to the development of highly oriented and extended polymer chains in a fiber spinning process. Fibers from liquid crystalline polymers were spun above the mesophase transition temperature. Linear thermotropic liquid crystalline polymers based on 4,4′-dihydroxy-2,2′-dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides have been previously studied by different techniques and their conformational properties are well established. In this work the mechanical properties of fibers based on such polymers were studied. High values of tenacity and tensile moduli were obtained. These values increase with molecular mass, but decrease with the length of the flexible spacer moiety. The spinning temperature is also an important parameter.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410511
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  • 3
    Electronic Resource
    Electronic Resource
    Fibers from flexible liquid crystal main-chain polymers. II. Functional copolymers based on the 4,4′-dihydroxy-2,2′-dimethylazoxybenzene mesogen and spacers based on 2-dodecenedioic and nonanedioic acids (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1009-1022 
    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: Fibers spun from liquid crystalline solutions or melts are characterized by a high degree of chain alignment which promotes high values of tenacity and tensile modulus in the direction of fiber axis but lower values in the transversal direction. Structural modifications are introduced into the flexible moiety and the mesogenic group to alleviate this shortcoming. The incorporation of a spacer based on 2-dodecenedioic acids into a thermotropic liquid crystalline polyester was studied. A phase diagram was established to optimize the composition of such copolyesters. A significant increase in mechanical properties on crosslinking through UV irradiation was observed. A remarkable property of such systems is the retention of molecular chain order in spite of temperatures in excess of Tg. This is valid for both crosslinked and uncrosslinked systems. Remarkable also is the crystallization on annealing of a number of copolymer compositions in spite of a structural difference between the comonomer units.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410512
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of carboxylated poly(butyl acrylate) latices produced by a semibatch process (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 585-594 
    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: Several carboxylated poly(butyl acrylate) latices prepared by a semibatch emulsion poly-merization process were characterized in this study. A significant amount of polyelectrolyte was found in the latex product containing 10% AA, designated as AA10. On the other hand, latices containing 0.1% AA (AA0.1), 0.1% MAA (MAAC.1), and 10% MAA (MAA10) showed very low levels of polyelectrolyte in water. Based on the critical flocculation concentration data, it can be concluded that incorporation of 10% AA or 10% MAA into the emulsion polymers can greatly improve the chemical stability of the latex products, especially at higher pH. The data of the pH and conductometric titration experiments show that the MAA unit can be distributed more uniformly in the latex particles in comparision with the AA unit. This result is further confirmed by determination of the Tg's of the emulsion polymers by means of thermally stimulated current (TSC). © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxygen transfer and mixing in a tower cycling fermentor (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 1557-1572 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Tower cycling fermentors for the production of single-cell protein from volatile substrates were studied. The mass transfer, mixing and circulation patterns, and residence time distribution (RTD) curves were investigated in these vessels. This study suggests that the tower cycling fermentors for volatile substrates fermentation may improve product yields and at the same time reduce the power consumption, thereby resulting in a significant increase in operating cost savings and capital profits. The results of this research further indicate a future potential for commercial scale tower cycling fermentors.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260181106
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  • 6
    Electronic Resource
    Electronic Resource
    Measuring diffusion coefficients by Taylor's method of hydrodynamic stability (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 2028-2033 
    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: Diffusion coefficients for liquid solutions can be measured using a hydrodynamic stability criterion first derived by G. I. Taylor. This method is used in the present work to determine diffusion coefficients for a range of solutes from small molecules to colloidal particles, at infinite dilution and at finite concentrations. The method is simple and accurate and seems to have wide applicability. Taylor's stability criterion can also be used to establish known, linear concentration gradients of several different solutes in one column of fluid, and one solute can be used to create a desired gradient of a second solute.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690321213
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  • 7
    Electronic Resource
    Electronic Resource
    In situ composite fibers: Blends of liquid crystalline polymer and poly (ethylene terephthalate) (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1533-1538 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: To augment the concept of in situ composites as alternatives to fiber-reinforced composites, polyblends of a thermotropic liquid crystalline polymer (LCP) and poly(ethylene terephthalate) (PET) were prepared. Fiber-spinning of the blends was performed on a piston-driven plastorneter. Blends of LCP and a low-intrinsic-viscosity PET resin showed poor mechanical performance, which was attributed to their processing behavior. Blends of LCP and a high intrinsicviscosity PET manifested an almost additive behavior with regard to tensile modulus and strength. Elongation of the blends, however, displayed a radical decline, which is reminiscent of fiber-reinforced composites. Heat treatment of the blend fibers modestly increased the tensile properties of the LCP-rich compositions. Blend fibers from PET-rich compositions exhibit a moderate decline in tensile properties owing to thermal relaxation of PET. The data demonstrate that in situ composites or blends of thermotropic LCPs and isotropic polymers present challenging alternatives to fiber-reinforced composite systems because of their ease of processing.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760312105
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