On the molecular origin of secondary relaxations in amorphous protic ionic conductor chlorpromazine hydrochloride — High pressure dielectric studies S. Hensel-Bielowka a, ⁎, K.L. Ngai b , A. Swiety-Pospiech c , L. Hawelek d , J. Knapik c , W. Sawicki e , M. Paluch c a Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, Poland b CNR-IPCF, Dipartimento di Fisica, Largo Bruno Pontecorvo 3,I-56127 Pisa, Italy c Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland d Institute of Non Ferrous Metals, Sowinskiego 5, 44-100 Gliwice, Poland e Department of Physical Chemistry, Medical University of Gdansk, Hallera 107, 80-416 Gdansk, Poland abstract article info Article history: Received 26 May 2014 Received in revised form 21 July 2014 Available online 22 August 2014 Keywords: Glass transition; Secondary relaxation; Ionic glasses; Dielectric spectroscopy; High pressure In this paper, we report the study of sub-T g dynamics of chlorpromazine hydrochloride. The substance is another pharmaceutical and glass-forming protic ionic conductor investigated by our group. We describe both ionic and dipolar behaviors and show the way in how to tell them apart. Mainly, we focus on the dynamics of the slower of the two secondary relaxation processes found. By means of the dielectric spectroscopy we study its behavior as a function of temperature and pressure. Moreover, on the basis of quantum-mechanical calculations, we designate the mechanism for faster secondary relaxation as the conformational change of the dimethylamine group. Finally, we compare the findings with data of lidocaine hydrochloride, procaine hydrochloride and procainamide hydro- chloride to answer the question of which features are typical for the protic ionic glasses and which are associated with specific chemical structure. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Recently we have studied the several protic ionic liquids (PILs) formed by proton transfer from a Brönsted acid to a Brönsted base [1], which include procainamide hydrochloride (procainamide HCl), procaine hydrochloride (procaine HCl) [2,3] and lidocaine hydro- chloride (lidocaine HCl) [4,5]. These PILs formed a subclass of glass- forming ionic conductors with beneficial properties in applications as pharmaceuticals. With the PILs having chemical bonding and structures different from ordinary molten salts and glassy ionic conductors, novel ionic conductivity relaxation properties can be expected to be observed together with ordinary behavior. In fact, results found in procaine HCl, procainamide HCl, and lidocaine HCl show interesting properties of ionic conductivity relaxation including the following examples. (1) There is decoupling of the ionic conductivity from the structural relax- ation responsible for glass transition [2–4] like that found in the molten salt 0.4Ca(NO 3 ) 2 –0.6KNO 3 (CKN) [6,7], and CdF 2 –LiF–AlF 3 –PbF 2 (CLAP) [8], and in room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM[PF 6 ]) [9–11]. (2) The complex electric modulus, M*(f)= M′(f)+ iM″(f), measured and used to characterize the dynamics of ions is well described by [12–15] M Ã ω ð Þ¼ M 0 þ iM ″ ¼ M ∞ 1- Z ∞ 0 dt exp -iωt ð Þ -dΦ=dt ð Þ 2 4 3 5 : ð1Þ In Eq. (1), M ∞ is the reciprocal of the high frequency dielectric con- stant ε ∞ , and Φ(t) is the Kohlrausch–Williams–Watts (KWW) stretched exponential function, Φ t ðÞ¼ exp - t τ σ T ðÞ   1-n σ   0 ≤n σ b1; ð2Þ where τ σ (T) is the conductivity relaxation time. The experimental elec- tric modulus loss peak M″(f) is well fitted by the M″(f) calculated by Eqs. (1) and (2) except on its high frequency side, where (2) there is ex- cess loss not accounted for by the fit. The excess loss is similar to that commonly found in molten, glassy and crystalline ionic conductors. However, in procaine HCl, procainamide HCl and lidocaine HCl the ex- cess loss of M″(f) at higher frequencies appears as a shoulder at temper- atures above the glass transition temperature T g , and a resolved loss peak in the glassy state. This faster secondary or β-conductivity relaxa- tion of M″(f) has relaxation time, τ σβ (T), which is shorter than the Journal of Non-Crystalline Solids 407 (2015) 81–87 ⁎ Corresponding author. E-mail address: stella.hensel-bielowka@us.edu.pl (S. Hensel-Bielowka). http://dx.doi.org/10.1016/j.jnoncrysol.2014.08.005 0022-3093/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol