par De Brouckère, Lucia ;Offergeld, Georges
Référence Bulletin des Sociétés chimiques belges, 67, 3-4, page (96-122)
Publication Publié, 1958
Article révisé par les pairs
Résumé : Dielectric constants and loss factors of various polyacrylic and polymethacrylic esters have been measured for frequencies ranging from .5 to 500 kilocycles/sec (in some cases to 14 megacycles/sec). The measurements covered a fairly wide temperature interval, both below and above the glass transition temperature Tg. In all cases a secondary, or β absorption band was found, which could not be attributed to cooperative movements of the chain segments. The dispersion curves could not be represented by the classical equation of Landell, Williams and Ferry, valid for the α bands. The energy of activation was lower for the β band than for the α, and for β bands this energy did not change abruptly at Tg. The β relaxation spectrum contrary to the α one, spreads out as the temperature is lowered. The β band seems to be due to movements of side groups, and when these are not too bulky the movements are not frozen at Tg. Copyright © 1958 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim