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Dielectric relaxations in polymers containing dioxacyclohexane rings by thermostimulated depolarization currents
Author(s) -
DíazCalleja Ricardo,
Jesús Sanchis Maria,
Aravena Milton,
Riande Evaristo,
Guzmán Julio
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200390007
Subject(s) - dielectric , glass transition , materials science , polymer , relaxation (psychology) , polymer chemistry , methyl group , natural rubber , depolarization , analytical chemistry (journal) , composite material , alkyl , organic chemistry , chemistry , medicine , psychology , social psychology , optoelectronics , endocrinology
The dielectric activity of poly{5‐[(methacryloxy)methyl]‐5‐ethyl‐1,3‐dioxacyclohexane} (PMAMED) and poly[(5‐methacryloxy)‐1,3‐dioxacyclohexane] (PMAD) in the glassy region and in the glass‐rubber transition is investigated by using global and partial thermostimulated discharge current (TSDC) techniques. The global TSDC curve for each polymer displays an ostensible β absorption in the glassy region followed in increasing order of temperature for a prominent α glass rubber relaxation. Partial depolarisation curves show in detail the regions of the glassy state in which more dielectric activity occurs. The TSDC curves for PMAMED are compared with those of its acrylate homologous, poly{5‐[(acryloxy)methyl]‐5‐ethyl‐1,3‐dioxacyclohexane} (PAMED), finding that the methyl group in the former polymer only hinders long range micro‐Brownian motions in the chains, thus shifting the glass‐rubber relaxation to higher temperatures, without affecting in a significant way molecular motions in the glassy region. Small changes in the neighbourhood of the 1,3‐dioxacyclohexane ring, such as suppression of a methylene group or replacement of the equatorial hydrogen in position 2 of the ring for a phenyl group, depresses the dielectric activity and shifts the β absorptions to lower temperatures. The interconversion between TSDC and a.c. dielectric results in the glassy region is discussed.