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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymer research 4 (1997), S. 17-24 
    ISSN: 1572-8935
    Keywords: Buckminsterfullerene C60 ; Poly(vinyl alcohol) ; Cyclic voltammetry ; Redox feasibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Poly(vinyl alcohol) (PVA) was reacted with strong base NaH to yield pendant oxy anions, followed with nucleophilic addition to C60. The resulted PVA(C60-Na+)n products were then converted to PVA(C60H)n by stirring with a strong acid cation exchanger of H+-form. Extraction of the C60-containing PVAs by toluene, which is a good solvent for C60, exhibits no color transfer to the toluene phase. The C60-containing PVAs were identified by the characteristic IR and UV-Vis absorptions of C60. The electrochemical behaviors in solution or in film state were investigated by cyclic voltammetric methods. The cyclic voltammogram of 4a shows a reduction peak at −2.30 V which should be due to the bonded C60 chromophores. In the film state, obtained by coating C60-containing PVA solution on graphite electrode, PVA(C60-Na+)n is much easily reduced and oxidized than PVA(C60H)n. Furthermore, the difference in this reduction and oxidation feasibility is enhanced with increasing C60 content. However, coating with PVA(C60H)n or PVA(C60-Na+)n reduces the redox ability of the graphite electrode.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2999-3008 
    ISSN: 0887-624X
    Keywords: 7,7′-coumarinyl polymethylene dicarboxylate ; photopolymerization ; fluorescence ; coumarin ; dimerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All eight 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylates (3, 4) containing terminal photoreactive coumarin chromophores show strong fluorescence intensities at room temperature in dimethyl sulfoxide (DMSO) and CH2Cl2. After irradiation with 350 nm light for 2 h, the fluorescence characteristics of the dicarboxylates reveal their photopolymerization paths. On irradiation of the unsubstituted dicarboxylates (3) in DMSO, singlet excited state excimers are formed, leading to syn head-to-head coumarin dimer configuration. However, for all dicarboxylates in CH2Cl2, the dimerization of the coumarin chromophore proceeds via a triplet excited state in the presence of benzophenone to form the anti-configuration photoproducts. Further confirmations of the reaction mechanism are made by kinetic studies. At high concentration, photopolymerization of 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylate (4c) obeys zero-order and first-order kinetics for coumarin chromophore and benzophenone, respectively. This is a powerful proof of the proposed mechanism of a triplet excited state reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2999-3008, 1997
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2705-2714 
    ISSN: 0887-624X
    Keywords: coumarin derivatives ; photodimerization ; photocleavage ; reversible ; pho-tosensitizer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four photoreactive coumarin derivatives were successfully synthesized from 7-hydroxy-coumarin and 7-hydroxy-4-methylcoumarin, i.e., 7-propionyloxy-4-methylcoumarin (M1), 7-palmitoyloxy-4-methylcoumarin (M2), 7-propionyloxycoumarin (M3), and 7-palmitoy-loxycoumarin (M4). Reversible photodimerization (350 or 300 nm) and photocleavage (254 nm) of these coumarin derivatives dispersed in poly(vinyl acetate) (PVAc) were investigated by tracing their UV absorbance variations at 310 nm. The M2 and M4 with long palmitoyl chain show much better photoreaction reversibility than M1 and M3 with short propionyl chain. Moreover, photodimerization rate (under 350 nm) of M2 is greater than 200 times of that of M1. This has been explained by the formation of suitable conformation for revers-ible photodimerization due to the hydrophobic interactions. Photodimerization of M2 is ca. 3 times quicker than that of M4, indicating 4-methyl substitution enhances pho-todimerization. The influence of photodimerization wavelength (350 and 300 nm) and photosensitizer (benzophenone) have also been investigated in detail. © 1995 John Wiley & Sons. Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 613-624 
    ISSN: 0887-624X
    Keywords: anti head-to-head 7-hydroxycoumarin dimer ; anti head-to-tail 7-hydroxy-4-methylcoumarin dimer ; polyurethane ; photocleavage ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six polyurethanes containing coumarin dimer components in the main chain have been prepared by polyaddition of diisocyanates with anti head-to-head 7-hydroxycoumarin dimer or anti head-to-tail 7-hydroxy-4-methylcoumarin dimer. 7-Acetoxycoumarin and 7-acetoxy-4-methylcoumarin were first prepared and then photodimerized under 350 nm UV light to give anti head-to-head 7-acetoxycoumarin dimer and anti head-to-tail 7-acetoxy-4-methylcoumarin dimer, respectively. After hydrolyzing under acidic conditions to 7-hydroxycoumarin dimer and anti head-to-head 7-hydroxycoumarin dimer, they were polymerized with aliphatic and aromatic diisocyanates in N,N-dimethylacetamide to give the polyurethanes. Addition of dibutyltin dilaurate (T-12) as catalyst increases the polymer yield with the viscosity remaining almost unchanged. It was also found that lithium chloride enhances both the yield and viscosity of the polyurethanes by increasing their solubility possibly through complexation. The polyurethanes are symmetrically photocleaved at cyclobutane rings under 254 nm UV light to dicoumarins. Reversible photodimerization of the photocleaved compounds have also been investigated under 300 and 350 nm UV light. The polyurethanes from aromatic diisocyanates or with 4-methyl substituent exhibit greater reactivity in the photocleavage reaction. © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1319-1327 
    ISSN: 0887-624X
    Keywords: coumarin dimer ; photocleavage ; trans-2,2′-dihydroxystilbene ; interfacial polycondensation ; photocrosslinking ; characteristic curve ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The monomer, trans-2,2′-dihydroxystilbene (DHS), has been prepared by asymmetric photocleavage (254 nm) of coumarin dimer acid derived from coumarin dimer. Four new polyesters are successfully synthesized by interfacial polycondensation of the DHS with adipoyl chloride, azelaoyl chloride, sebacoyl chloride, and dodecanedioyl dichloride, respectively. The reduced viscosities of the polyesters decrease from 0.32 to 0.11 dL/g as the number of methylene unit in diacid chlorides increases from 4 to 10. From DSC investigation, it is found that the polyesters are semi-crystalline polymers with Tm = 39-192°C. Under 350 nm light, photocrosslinking behavior in solution and film-state is investigated by UV spectral change with irradiation time (350 nm). The photoreactive stilbene chromophores in the main chain dimerize to form cyclobutane derivatives, and lead to crosslinking of the polyesters. Photosensitivity in the film state has also been evaluated by their characteristic curves. Polyester from dodecanedioyl dichloride (5d) exhibits the highest initial reaction rate and ultimate crosslinking ratio. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 255-263 
    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 novel ionomer was successfully prepared by lactone ring opening of stryrene-coumarin copolymer, containing 9.28 mol % of coumarin, with aqueous NaOH solution. Its solution properties in methanol, including reduced viscosity and surface tension, were investigated as a function of temperature, concentration, and pH value. The reduced viscosities of the ionomer solution decrease smoothly with increasing temperature and concentration. Moreover, the viscosities of the ionomer solution (0.3 g/dL MeOH) are ca. twofold of the copolymer solution (0.3 g/dL THF) between 25 and 45°C. It increases from ca. 0.14 to 0.59 dL/g as pH value decreases from 10.6 to 6, then decreases slightly and reaches a constant value of 0.47 dL/g below pH 4.7. The surface tension of methanol solution decreases with increasing concentration and reaches an asymptotic value of 24.1 dyne/cm as the concentration is above 0.50 g/dL due to the surface-active effects. These properties can be related to the balance between hydrogen bonding and charge-charge interactions that occur along the ionomer backbone. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 277-283 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of Zn(II), Cd(II), and Hg(II) incorporation into meso tetrameta-tolueneporphyri n (H2T(m-CH3)PP) in acetone have been studied by means of stopped-flow method. A unified reaction mechanism was proposed and the kinetic parameters were obtained by nonlinear least-square methods. The effect of ionic strength (I) on Cd(II)/H2T(m-CH3)PP was investigated. It has been found that there is a negative kinetic salt effect and the relationship of rate constants with ionic strength was obtained. Some solvent effects have also been investigated in this article. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 277-283, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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