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Molecular Dynamics in Amorphous Atropine and Tolnaftate

Author Affiliations

  • 1Department of Physics, University of Calicut, Kerala, India
  • 2MES Ponnani College, Ponnani, India
  • 3Department of Physics, University of Calicut, Kerala, India
  • 4Departmento di Fisica, Università di Pisa, Italy

Res. J. Recent Sci., Volume 5, Issue (3), Pages 40-44, March,2 (2016)


During the development of new pharmaceutical products in amorphous form, the molecular mobility of amorphous active ingredients has to be characterized in detail. Here, using broadband dielectric spectroscopy, the molecular mobility in supercooled liquid and glassy states of two pharmaceuticals namely atropine and tolnaftate have been studied. The dielectric permittivity and loss spectra of glassy and ultraviscous states of the above two pharmaceuticals have been measured for some test frequencies over a wide temperature range. Above the glass transition temperature Tg, the presence of the structural α- relaxation peak was observed which shifts towards lower frequencies as the temperature decreases and kinetically freezes at Tg. The secondary relaxations perceivable below the glass transition temperature is due to intramolecular modes and are usually designated as β, γ and δ etc. are clearly observed in the ε” spectra of atropine, while in tolnaftate no secondary relaxation processes is observed in the loss spectra, but an excess contribution to the high- frequency tail of the α-peak, called excess wing is observed. The α- process shows non-Arrhenius behavior for both the samples. The dielectric relaxation time increases on cooling according to the Vogel-Fulcher-Tammann equation. The secondary relaxation process shows Arrhenius behavior.


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