Molecular mobility of amorphous N-acetyl-α-methylbenzylamine and Debye relaxation evidenced by dielectric relaxation spectroscopy and molecular dynamics simulations. Issue 2 (13th December 2018)

• Record Type: Journal Article
• Authors: Atawa, Bienvenu; Correia, Natália T.; Couvrat, Nicolas; Affouard, Frédéric; Coquerel, Gérard; Dargent, Eric; Saiter, Allisson
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 2(2018)
• Page Start: 702
• Page End: 717
• Publication Date: 2018-12-13
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp04880k
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Molecular mobility of NAC-MBA molecule is described by means of DRS, FSC and MD simulations. Abstract : The present work focusses on the molecular mobility characterization of amorphous N -acetyl-α-methylbenzylamine (Nac-MBA) by Broadband Dielectric Relaxation Spectroscopy (DRS) coupled with Fast Scanning Calorimetry (FSC) and Molecular Dynamics (MD) simulations covering over 12 decades in the frequency range. This study reveals another example of a secondary amide that shows a very intense Debye-like contribution (almost 90% of the global dielectric intensity) in addition to the structural α-relaxation and secondary Johari–Goldstein β-relaxation. The D- and α-relaxations are separated by about one decade (in frequency) and their relaxation times follow a near parallel temperature evolution (Vogel–Fulcher–Tammann–Hesse). The micro-structure of Nac-MBA has been investigated from MD simulations. It is shown that the intense Debye-like process emanates from the formation of linear intermolecular H-bonding aggregates (precursors of the crystalline structure) generating super-dipole moments.