Molecular mobility of amorphous N-acetyl-α-methylbenzylamine and Debye relaxation evidenced by dielectric relaxation spectroscopy and molecular dynamics simulations.

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).

Impact of chirality on the Glass Forming Ability and the crystallization from the amorphous state of 5-ethyl-5-methylhydantoin, a chiral poor glass former.

The investigation of the glassy state of 5-ethyl-5-methylhydantoin (i.e. 12H, a chiral Active Pharmaceutical Ingredient) was attempted by Differential Scanning Calorimetry (DSC) and Fast Scanning Calorimetry (FSC).

Glass transition of anhydrous starch by fast scanning calorimetry.

By means of fast scanning calorimetry, the glass transition of anhydrous amorphous starch has been measured. With a scanning rate of 2000Ks, thermal degradation of starch prior to the glass transition has been inhibited. To certify the glass transition measurement, structural relaxation of the glassy state has been investigated through physical aging as well as the concept of limiting fictive temperature.

Correlated and cooperative motions in segmental relaxation: Influence of constitutive unit weight and intermolecular interactions.

This work clarifies the notion of correlated and cooperative motions appearing during the α-relaxation process through the role of the molecular weight of the constitutive units and of the interchain dipolar interactions. By studying amorphous copolymers of poly(ethylene-co-vinyl acetate) with different vinyl acetate contents, we show that the correlated motions are not sensitive to the interchain dipolar interactions, in contrast to the cooperative motions, which increase with a strengthening of the intermolecular interactions for this sample family. Concerning the influence of the molecular weight m_{0}, the notion of "correlated motions" seems to be equivalent to the notion of "cooperative motions" only for low m_{0} systems.

Water barrier properties in biaxially drawn poly(lactic acid) films.

Crystallization is among the easiest ways to improve polymer barrier properties because of the tortuosity increase within the material and the strong coupling between amorphous and crystalline phases. In this work, poly(lactic acid) (PLA) films have undergone α' thermal crystallization or different drawing processes. Although no effect of α' thermal crystallization on water permeability is observed, the drawing processes lead to an enhancement of the PLA barrier properties.