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wizyta

od 2020-09-20


Authors: Adrjanowicz K., Kamiński K., Dulski M., Włodarczyk P., Bartkowiak G., Popenda Ł., Jurga S., Kujawski J. Kruk J., K. Bernard M., Paluch M.

Title: Synperiplanar to antiperiplanar conformation changes as underlying the mechanism of Debye process in supercooled ibuprofen

Source: Journal of Chemical Physics

Year : 2013


Abstract:

In this Communication, we present experimental studies that put new insight into the puzzling nature of the Debye relaxation found in the supercooled liquid state of racemic ibuprofen. The appearance of D-relaxation in the loss spectra of non-hydrogen bonding methylated derivate of ibuprofen has proven that Debye relaxation is related solely with conformational changes of the carboxyl group, termed in this paper as synperiplanar-antiperiplanar. Our studies indicate that the presence of hydrogen bonding capabilities is not here the necessary condition to observe Debye process, however, their occurrence might strongly influence α- and D-relaxations dynamics. Interestingly, the activation energy of the D-process in ibuprofen methyl ester on approaching Tg was found to be perfectly consistent with that reported for ibuprofen by Affouard and Correia [J. Phys. Chem. B 114, 11397–11402 (2010)] (∼39 kJ/mol). Finally, IR measurements suggest that the equilibrium between conformers concentration depends on time and temperature, which might explain why the appearance of D-relaxation in supercooled ibuprofen depends on thermal history of the sample.
(C) 2013 AIP Publishing LLC.

DOI: 10.1063/1.4820492   (Pobrane:  2020-10-25)

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