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  • 1
    Electronic Resource
    Electronic Resource
    Intramolecular formation of excimers in model compounds for polyesters obtained from 2,6-naphthalene dicarboxylic acid and cyclohexanediols (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1511-1519 
    Details
    ISSN: 0887-6266
    Keywords: conformation ; excimer ; fluorescence ; hairpins ; polyester ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence in dilute solution has been measured as a function of solvent viscosity for four bichromophoric models for polyesters with naphthalene in the rigid aromatic unit and diols derived from cyclohexane as the flexible spacer. The spacers are 1,2-cis-cyclohexanediol, 1,2-trans-cyclohexanediol, a 1:2 mixture of 1,3-cis- and 1,3-trans-cyclohexanediols, and a 1:2 mixture of 1,4-cis- and 1,4-trans-cyclohexanediols. The shape of the emission spectra for the molecules in this series is less sensitive to the viscosity of the medium than was the case for an analogous series in which a methylene or oxyethylene spacer replaces the cyclohexanediol spacer. The dependence of the excimer emission on the type of spacer is different also in the series in which the rigid units contain naphthalene or benzene. When the rigid units contain naphthalene, excimer formation is maximal if the spacer contains 1,2-trans-cyclohexanediol, but this spacer produces a molecule with a very small tendency for excimer formation in its polymers with terephthalate. A conformational analysis correctly concludes that the spacer most conducive to excimer formation should be 1,2-trans-cyclohexanediol, but it does not identify the correct order of the remaining three bichromophoric model compounds. The problem may reside in the method for taking into account the finite width of the torsional well associated with each rotational isomer. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320823
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  • 2
    Electronic Resource
    Electronic Resource
    Intramolecular formation of excimers in model compounds for polymers of 2,6-naphthalene dicarboxylic acid and five glycols in media of different viscosity (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2623-2633 
    Details
    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; naphthalene ; polyester ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady-state fluorescence has been used to study the dependence of the intramolecular formation of excimers in media of differing viscosity, η, for model compounds of polyesters containing naphthalene groups. The model compounds are derived from 2-naphthalene carboxylic acid as rigid units and glycols, HO (SINGLEBOND) (CH2)m (SINGLEBOND) OH, m = 2(SINGLEBOND) 6, as flexible spacers. The ratio of the intensity of excimer and monomer emissions, ID/IM, exhibits two regimes: a regime at high η where ID/IM shows an odd(SINGLEBOND) even effect with m, with maxima at odd m, and a regime at low η where the odd-even effect is lost, and the maximum values are obtained for m = 3 and 6. Calculations performed for the equilibrium state using the rotational isomeric state model and Molecular Dynamics (MD) simulations allow the rationalization of the behavior of ID/IM with m in the media of high and low η, respectively. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Rationalization of the ratio of excimer-to-monomer fluorescence emission intensity in bichromophoric diesters of 1-pyrenoic acid and mono-, di-, tri-, and tetraethylene glycols (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1107-1116 
    Details
    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; polyester ; pyrene ; rotational isomeric state model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ratio of excimer to monomer emission intensities, denoted by ID/IM, was measured for Py-COO(CH2CH2O)mCO — Py, where Py denotes the 1-pyrenyl group and m = 1-4, in solvents of different viscosity, η. Three different systems were used to change the viscosity of the medium: (a) Mixtures of methanol and ethylene glycol at 25°C, (b) linear aliphatic alcohols, H(CH2)nOH, where n =1-6, also at 25°C, and (c) ethylene glycol over the range 6.6-35°C. The ratio ID/IM decreases sharply as η increases, and the rate of the decrease in ID/IM is a function of m. Quantitatively, the dependence of ID/IM on η at high viscosity, i.e., the slope [d(ID/IM)/d(1/η)]∞, is larger in the present work than in another series of 1-pyrenyl diesters in which the flexible spacer is an oligomer of polyethylene, instead of an oligomer of polyoxyethylene. In the limit where η → ∞, the ratio ID/IM assumes its largest value in the bichromophoric compound with m = 2. However, as η decreases the compound with m = 3 becomes the one with the largest ID/IM. A complete rotational isomeric state analysis (for the compounds with m = 1-3) and a Monte Carlo simulation (for the compound m = 4) of the conformations of the diesters can rationalize the behavior of ID/IM in the high viscosity limit. ©1995 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330714
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  • 4
    Electronic Resource
    Electronic Resource
    Conformation of the ground-state dimer in poly(ethylene terephthalate) (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 207-212 
    Details
    ISSN: 0887-6266
    Keywords: dimer ; fluorescence ; PET ; poly(ethylene terephthalate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Absorbance, excitation, and emission measurements have been performed with methyl benzoate and five model compounds, C6H5COO (CH2)xOOCC6H5, x = 2-6. Under appropriate conditions, three of the model compounds (those with x = 3, 4, 5) show evidence for the formation of intramolecular ground-state dimers. The model compound with x = 5 can form two types of dimers which emit with different energies. The model compound with x = 3 forms one of these dimers, and the model compound with x = 4 prefers the other ground-state dimer. Molecular modeling of the dimers suggests that the two conformations of the ground-state dimers differ in the orientation of the two C=O bonds. In the one dimer these two bonds are nearly parallel, but in the other they make an angle of about 120°. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310209
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of the directionality of the ester group on the formation of hairpins in polyesters containing naphthalene and a flexible spacer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1127-1133 
    Details
    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; molecular dynamics ; naphthalene ; polyester ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady-state fluorescence measurements and molecular dynamics simulations have been used to study the intramolecular formation of excimers in five model compounds for polyesters containing naphthalene groups separated by flexible spacers. The model compounds are derived from 2-hydroxynaphthalene and HOOC—(CH2)n—COOH, n = 2-6. The ratio of the intensity of excimer and monomer emissions, ID/IM, is nearly independent of the viscosity of the medium, η, over the range covered in dilute solution. Although ID/IM is always very small, it shows an odd-even effect for the first four members of the series, with maxima when n is odd. Molecular dynamics simulations provide an explanation for the small values of ID/IM, their weak dependence on η, and the trend of ID/IM with n. The results for the present series of model compounds are compared with previous work, which reported larger values of ID/IM, and a stronger dependence of ID/IM on η, for bichromophoric compounds derived from 2-naphthoic acid and aliphatic glycols, where the direction of the ester groups is reversed. The origin of the difference in the behavior of ID/IM in the two series is identified. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1127-1133, 1997
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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