Intra- and Intermolecular Inhomogeneities in the Course of Glassy Densification of Polyalcohols

TL;DR

This study uses infrared spectroscopy to investigate molecular and intermolecular inhomogeneities during the glassy densification of polyalcohols, revealing significant inter-molecular inhomogeneities that influence the densification process.

Contribution

It provides new insights into the roles of intra- and inter-molecular inhomogeneities in glassy densification, challenging assumptions of uniform molecular expansion.

Findings

Intra-molecular expansion is negligible during densification.

Severe inter-molecular inhomogeneities are observed.

Inter-molecular inhomogeneities play a key role in glassy densification.

Abstract

To test basic assumptions inherent to most theories of molecular liquids and glasses, Infrared spectroscopy is carried out on short polyalcohols at temperatures ranging from far above to far below their glass transition. By analyzing specific vibrations, the thermal expansion of covalent bonds and hydrogen bridges is determined revealing striking differences. A comparison with density verifies the negligibility of \textit{intra}molecular expansion but exposes severe inhomogeneities on \textit{inter}molecular scale. This signals distinct roles in glassy densification and promotes an atomistic understanding.