Molecular dynamics in amorphous pharmaceutically important protic ionic liquid–benzalkonium chloride

• Published in: Journal of molecular liquids 2018-02, Vol.251, p.487-491
• Main Authors: K.P., Safna Hussan, Thayyil, Mohamed Shahin, M., Binesh, Deshpande, S.K., K. Rajan, Vijisha
• Format: Article
• Language: English
• Subjects: Active pharmaceutical ingredients; Amorphous materials; Broadband dielectric spectroscopy; Density function theory; Glass transition; Protic ionic liquids; Thermodynamic parameters
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2017.12.007

In this paper, we report the dielectric measurements at ambient pressure to portray the molecular dynamics of a glass forming pharmaceutical as well as a protic ionic conductor, benzalkonium chloride [BaCl] by means of broadband dielectric spectroscopy. The measurement in macroscopic nature of a stochastic transport theory and of the electric modulus formalism stanchly reproduces the shape of the dispersion of the microscopic ionic movement in terms of translational and ionic diffusive motion of molecular ions. The situation is analogous to most ionic conductors, BaCl showed only single resolved peak in the electric modulus formalism and doesn't show any crystallisation tendency during cooling as well as heating. The temperature dependence of the conductivity relaxation has been fitted by single Vogel–Fulcher–Tamman (VFT) equation. It is found that the value of Tg observed from DSC is significantly higher than one obtained from the α-conductivity relaxation corresponding to 100s indicating that the structural τα(Τ) is longer than conductivity τσα(Τ) for about 10K. Finally, the results were compared with data for other protic ionic conductors like Procaine HCl, Procainamide HCl, Verapamile HCl, Lidocaine HCl, Tramadole HCl and Chlorpromazine HCl and found that BaCl is a good strong glass former. [Display omitted] •BaCl doesn't show any crystallisation tendency during cooling as well as heating.•Tg from DSC is significantly higher than one from the α-conductivity relaxation.•The results were compared with data for other protic ionic conductors.•The KWW fit and thermal analysis from DSC shows BaCl is strong glass former.