Determination of Young's Modulus of Active Pharmaceutical Ingredients by Relaxation Dynamics at Elevated Pressures

J Phys Chem B. 2020 Nov 19;124(46):10500-10506. doi: 10.1021/acs.jpcb.0c05523. Epub 2020 Nov 8.

Abstract

A new approach is theoretically proposed to study the glass transition of active pharmaceutical ingredients and a glass-forming anisotropic molecular liquid at high pressures. We describe amorphous materials as a fluid of hard spheres. Effects of nearest neighbor interactions and cooperative motions of particles on glassy dynamics are quantified through a local and collective elastic barrier calculated using the elastically collective nonlinear Langevin equation theory. Inserting two barriers into Kramer's theory gives the structural relaxation time. Then, we formulate a new mapping based on the thermal expansion process under pressure to intercorrelate particle density, temperature, and pressure. This analysis allows us to determine the pressure and temperature dependence of α relaxation. From this, we estimate the effective elastic modulus of amorphous materials and capture the effects of conformation on the relaxation process. Remarkably, our theoretical results agree well with experiments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Elastic Modulus
  • Glass*
  • Molecular Conformation
  • Pharmaceutical Preparations*
  • Temperature

Substances

  • Pharmaceutical Preparations