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Polydiacetylene chains diluted in their single-crystal monomer matrix (1994)

Spagnoli, S. ; Berréhar, J. ; Lapersonne-Meyer, C. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 100 (1994), S. 6195-6202

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The spectroscopic properties of the chains of the polydiacetylene (PDA) poly-4BCMU, diluted in their single-crystal monomer matrix are studied and discussed in terms of the single polymer chain electronic properties, the monomer structural changes, and their mutual influence. The polymer exciton transition energy shifts considerably (by 0.3 eV) as temperature decreases, down to a value that may be the lowest transition energy yet observed in a PDA. Two first-order structural transitions of the monomer crystal are observed near 320 and 220 K. They show up in the polymer spectroscopic properties—absorption and resonance Raman scattering—as discontinuities of both wave numbers and linewidths. So, the polymer chains behave as probes of the monomer crystal structural changes. A new electronic transition is observed below the main exciton one, possibly corresponding to a state of g symmetry. A weak fluorescence is observed at low temperature. Its origin coincides with the exciton absorption. Therefore, there is no configurational relaxation in the exciton state during the fluorescence lifetime.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.467082

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Simultaneous distillation-extraction and dynamic headspace methods in the gas chromatographic analysis of Parmesan cheese volatiles (1994)

Careri, M. ; Manini, P. ; Spagnoli, S. ; [et al.]

Springer

Chromatographia 38 (1994), S. 386-394

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ISSN: 1612-1112

Keywords: Gas chromatography-mass spectrometry ; Dynamic headspace sampling ; Simultaneous steam distillation-extraction ; Parmesan cheese

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Summary Dynamic headspace and simultaneous steam distillation-extraction techniques were used to isolate volatile components of Parmesan cheese. Identification of the substances was carried out by GC and GC-MS; 110 compounds were identified in the samples obtained using the headspace technique, 105 in the extracts; among them, about 50 compounds were isolated with both procedures. Mass spectral data showed evidence for a number of newly reported compounds such as 3-(methylthio)propanal, δ-tetradecalactone, 9-tetra-decenoic and 9-hexadecenoic acids. Mass spectra of some compounds are discussed and a comparison between the results obtained with the two sampling methods is given.