Comparison of electron spin resonance probe and dielectric relaxation in physically and chemically crosslinked polymers

✍ Scribed by Michael Reinhardt; Andreas Schönhals; Dietmar Pfeifer; Karl Pfeiffer; Irene V. Lampe; Hans-Joachim Lorkowski

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 769 KB
• Volume: 7
• Category: Article
• ISSN: 1042-7147
• DOI: 10.1002/(sici)1099-1581(199610)7:10<791::aid-pat588>3.0.co;2-0

✦ Synopsis

Dielectric relaxation s ectroscopy in the frequency range from 1O-'Hz to 10 Hz and electron spin resonance (ESR) experiments are employed to study the dynamics in chemically and physically crosslinked networks. As examples for physically crosslinked networks ortho-and para-cresol nouolacs were investigated. Dielectrically these materials show low-temperature 6and high-temperature a-relaxation. Both relaxation regions differ for both types of novolacs. This is also refIected by the ESR measurements and is discussed in terms of different hydrogen bonds found to be stronger in para-cresol nouolac. For the chemically crosslinked poly(trially1 isocyanurate) only a p-peak is found by the dielectric measurements. Also in the ESR experiment the slow motion regime is characterized up to high temperatures. This means that the segmental motion is strongly suppressed by chemical crosslinking. Nevertheless the obtained change in the formal TSoG value can be used to characterize the glass transition in highly crosslinked systems by the ESR method. l ?