Study on Glass Transition Temperature of Amorphous Polymer Thin Film

Abstract

The glass transition temperaure Tg of amorphous polymer thin film was investigated. The opposite experimental results, the increase or decrease in Tg of thin film with decreasing film thickness, were found. It was believed that the free surface near the polymer-air interface has a smaller chain ends density, leading to the decrease in Tg; while the polymer-substrate interface has a larger chain ends density, resulting in the increase in Tg. However, there are a competition between the both, and the interaction of polymer and substrate is a dominant factor to affect Tg of thin film. In addition, the multilayer model of thin film was proposed to explain the effect of the free surface and the interface on the Tg of thin film.