Some Aspects of Dielectric Relaxation of Amorphous Polymers Including the Effects of a Hydrostatic Pressure

Abstract

The dielectric relaxation of amorphous polymers has been extensively studied as a function of frequency and temperature [1, 2], and in recent years studies have been made using applied pressure as an additional variable [3 – 13]. The general feature that emerges is that many amorphous polymers exhibit two relaxation regions, α and β, at low temperatures which appear to coalesce at higher temperatures forming what we shall term the (α β) process [5, 7, 11. The α relaxation is due to the microbrownian motions of chains and is associated with the polymer glass transition. The origin of the β process is less certain, but it is thought to be due to side group motion in polymers having flexible dipolar side groups [1,2] and due to local mode motions in chains that do not possess flexible side groups [1, 2]. It has been suggested that the (α β) process is due to overall motions of the coupled repeat units along a chain and in this way would be regarded as a continuation of the α process to higher temperatures [13] It has also been suggested [14] that the (α β) process should be regarded as a β process.