Molecular dynamics in nanostructured polyimide-silica hybrid materials and their thermal stability

Bershtein, VA; Egorova, LM; Yakushev, PN; Pissis, P; Sysel, P; Brozova, L

dc.contributor.author	Bershtein, VA	en
dc.contributor.author	Egorova, LM	en
dc.contributor.author	Yakushev, PN	en
dc.contributor.author	Pissis, P	en
dc.contributor.author	Sysel, P	en
dc.contributor.author	Brozova, L	en
dc.date.accessioned	2014-03-01T01:18:04Z
dc.date.available	2014-03-01T01:18:04Z
dc.date.issued	2002	en
dc.identifier.issn	0887-6266	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/14779
dc.subject	nanocomposites	en
dc.subject	polyimides	en
dc.subject	molecular dynamics	en
dc.subject	glass transition	en
dc.subject	thermal properties	en
dc.subject.classification	Polymer Science	en
dc.subject.other	SOL-GEL PROCESS	en
dc.subject.other	CREEP RATE SPECTROSCOPY	en
dc.subject.other	GLASS-TRANSITION	en
dc.subject.other	LASER INTERFEROMETER	en
dc.subject.other	POLYMER HYBRIDS	en
dc.subject.other	LIQUIDS	en
dc.subject.other	RELAXATION	en
dc.subject.other	FILMS	en
dc.subject.other	POLYSTYRENE	en
dc.subject.other	MEMBRANES	en
dc.title	Molecular dynamics in nanostructured polyimide-silica hybrid materials and their thermal stability	en
heal.type	journalArticle	en
heal.identifier.primary	10.1002/polb.10162	en
heal.identifier.secondary	http://dx.doi.org/10.1002/polb.10162	en
heal.language	English	en
heal.publicationDate	2002	en
heal.abstract	Molecular motion and thermal stability in two series of nanophase-separated polyimide-silica (PI-SiO2) hybrid materials with chemically bound components were studied. The hybrids were synthesized from p-aminophenyltrimethoxysilane-terminated poly(amic acid)s as PI precursors and tetramethoxysilane as a silica precursor via a sol-gel process. The hybrids differed in their PI chemical structure and chain length (number-average molecular weight = 5.000, 7.500, or 10.000) and in their SiO2 content, which ranged from 0 to 50 wt %. Differential scanning calorimetry, laser-interferometric creep rate spectroscopy, and thermally stimulated depolarization current techniques were used for studying the dynamics from 100 to 650 K and from 10(-3) to 10(-2) Hz. Comparative thermogravimetric measurements were also carried out from 300 to 900 K. Silica nano- or submicrodomains that formed affected PI dynamics in two opposite directions. Because of the loosening of the molecular packing of PI chains confined to nanometer-scale spaces between silica constraints, an enhancement of small-scale motion, mostly at temperatures below the beta-relaxation region, occurred. However, a partial or total suppression of segmental motion could be observed above the beta-relaxation temperature, drastically so for the shortest PI chains at elevated silica contents and within or close to the glass-transition range, because of the covalent anchoring of chain ends to silica domains. Large changes in thermal stability, including a 2.5-fold increase in the apparent activation energy of degradation, were observed in the hybrids studied. A greater than 100 degreesC rise in long-term thermal stability could be predicted for some hybrids with respect to pure PI. (C) 2002 Wiley Periodicals, Inc.	en
heal.publisher	JOHN WILEY & SONS INC	en
heal.journalName	JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS	en
dc.identifier.doi	10.1002/polb.10162	en
dc.identifier.isi	ISI:000175073800014	en
dc.identifier.volume	40	en
dc.identifier.issue	10	en
dc.identifier.spage	1056	en
dc.identifier.epage	1069	en