Conformational probes in study of glassy polymers

Abstract

This work is devoted to development of FTIR spectroscopic method of conformational probes in glassy polymers. A new approach is employed to model the freezing of conformational transitions in probe molecules in glassy polymers. This method is based on introducing small molecules (probes) in a polymer and following conformational dynamics in the probe molecules at different temperatures. For each polymer-probe system, freezing of conformational transitions is observed by FTIR at a certain individual temperature, Tf. A linear correlation between the freezing temperature Tf of conformational transitions of probe molecules and the size of rotational fragments of probe molecules is observed. The magnitude of Tf increases with the size of rotational fragments of the probe molecules and decreases with the free volume fraction of the studied polymers. The obtained results were interpreted in terms of existing "mobile" and "fixed" free volume entities in glassy polymers. The new representations about the processes occurring in polymeric matrices at Tf are given. Finally, relaxation transitions observed in the polymers at the temperatures Tf were assigned to certain types of molecular mobility of their lateral groups. © 2006 Elsevier B.V. All rights reserved.