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

Bershtein, VA; Egorova, LM; Yakushev, PN; Georgoussis, G; Kyritsis, A; 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	Georgoussis, G	en
dc.contributor.author	Kyritsis, A	en
dc.contributor.author	Pissis, P	en
dc.contributor.author	Sysel, P	en
dc.contributor.author	Brozova, L	en
dc.date.accessioned	2014-03-01T01:14:49Z
dc.date.available	2014-03-01T01:14:49Z
dc.date.issued	1999	en
dc.identifier.issn	1022-1360	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/13237
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-0033264287&partnerID=40&md5=40c2cbfca94921f1699f556785495c10	en
dc.subject.classification	Polymer Science	en
dc.subject.other	SOL-GEL PROCESS	en
dc.subject.other	LASER INTERFEROMETER	en
dc.subject.other	POLYMERS	en
dc.subject.other	RELAXATIONS	en
dc.title	Molecular dynamics in nanostructured polyimide-silica hybrid materials and their thermal stability	en
heal.type	journalArticle	en
heal.language	English	en
heal.publicationDate	1999	en
heal.abstract	Molecular motion and thermal stability in two series of nanophase-separated polyimide-silica (PI-SiO2) hybrid networks with chemically bound components were studied. The hybrids were prepared via a sol-gel process and differed in PI structure and chain length, and in SiO2 content ranging from 10 to 50 wt.%. Differential scanning calorimetry, laser-interferometric creep rate spectroscopy, dielectric relaxation spectroscopy, thermally stimulated depolarization current techniques, anp thermogravimetry were used covering, on the whole, the ranges of 100-900 K and 10(-3)-10(9) Hz. Silica domains influenced PI dynamics in two opposite directions. Loosened segmental packing in chains confined to nanovolumes resulted mainly in rise of small-scale motion below beta-relaxation region, while anchoring of chain ends to 'rigid walls' caused, contrarily, a partial or total suppression of segmental motion above T-beta, especially drastically at the temperatures close to and within glass transition. The latter resulted in a large change in thermal stability, e.g., 2.5-fold increasing of the apparent activation energy of thermooxidative degradation, and more than 100(0) rise of predicted long-term thermal stability for the hybrids as compared to that for PI.	en
heal.publisher	WILEY-V C H VERLAG GMBH	en
heal.journalName	Macromolecular Symposia	en
dc.identifier.isi	ISI:000085544300003	en
dc.identifier.volume	146	en
dc.identifier.spage	9	en
dc.identifier.epage	15	en