Structure and molecular dynamics of hyperbranched polymeric systems with urethane and urea linkages

Kyritsis, A; Raftopoulos, K; Rehim, MA; Shabaan, ShS; Ghoneim, A; Turky, G

dc.contributor.author	Kyritsis, A	en
dc.contributor.author	Raftopoulos, K	en
dc.contributor.author	Rehim, MA	en
dc.contributor.author	Shabaan, ShS	en
dc.contributor.author	Ghoneim, A	en
dc.contributor.author	Turky, G	en
dc.date.accessioned	2014-03-01T01:31:59Z
dc.date.available	2014-03-01T01:31:59Z
dc.date.issued	2009	en
dc.identifier.issn	0032-3861	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20007
dc.subject	Dielectric spectroscopy	en
dc.subject	Hyperbranched polymers	en
dc.subject	Polyurethanes	en
dc.subject.classification	Polymer Science	en
dc.subject.other	Aliphatic structures	en
dc.subject.other	Arrhenius	en
dc.subject.other	Broadband dielectric relaxation spectroscopy	en
dc.subject.other	Charge mobilities	en
dc.subject.other	Chemical structure	en
dc.subject.other	Conduction Mechanism	en
dc.subject.other	Dc conductivity	en
dc.subject.other	End groups	en
dc.subject.other	Glassy state	en
dc.subject.other	High activation energy	en
dc.subject.other	High conductivity	en
dc.subject.other	Hyperbranched	en
dc.subject.other	Hyperbranched polymers	en
dc.subject.other	Hyperbranched polyurethane	en
dc.subject.other	Molecular motions	en
dc.subject.other	One-pot method	en
dc.subject.other	Polar groups	en
dc.subject.other	Polymeric systems	en
dc.subject.other	Polyureas	en
dc.subject.other	Relaxation mechanism	en
dc.subject.other	Secondary relaxations	en
dc.subject.other	Temperature dependence	en
dc.subject.other	Thermal gravimetric analysis	en
dc.subject.other	Thermally stimulated depolarization currents	en
dc.subject.other	Activation energy	en
dc.subject.other	Aromatic polymers	en
dc.subject.other	Chromatographic analysis	en
dc.subject.other	Dendrimers	en
dc.subject.other	Dielectric devices	en
dc.subject.other	Dielectric losses	en
dc.subject.other	Dielectric spectroscopy	en
dc.subject.other	Differential scanning calorimetry	en
dc.subject.other	Gelation	en
dc.subject.other	Glass transition	en
dc.subject.other	Gravimetric analysis	en
dc.subject.other	Molecular dynamics	en
dc.subject.other	Nuclear magnetic resonance	en
dc.subject.other	Nuclear magnetic resonance spectroscopy	en
dc.subject.other	Organic polymers	en
dc.subject.other	Polymer blends	en
dc.subject.other	Polymers	en
dc.subject.other	Polyurethanes	en
dc.subject.other	Reconnaissance aircraft	en
dc.subject.other	Temperature distribution	en
dc.subject.other	Urea	en
dc.subject.other	Conducting polymers	en
dc.subject.other	dielectric property	en
dc.subject.other	monomer	en
dc.subject.other	polymer	en
dc.subject.other	polyurethane	en
dc.subject.other	structural property	en
dc.subject.other	thermal conductivity	en
dc.title	Structure and molecular dynamics of hyperbranched polymeric systems with urethane and urea linkages	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.polymer.2009.06.037	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.polymer.2009.06.037	en
heal.language	English	en
heal.publicationDate	2009	en
heal.abstract	Two series of hyperbranched polymers (HP), polyurethanes and polyureas, with aromatic and aliphatic structures, are synthesized in one-pot method using commercially available monomers. The obtained HP samples were characterized by H-1 Nuclear Magnetic Resonance (NMR) spectroscopy, Gel Permeation Chromatography (GPC), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) measurements. Molecular dynamics in these systems were investigated by combining Thermally Stimulated Depolarization Currents (TSDC) and broadband Dielectric Relaxation Spectroscopy (DRS) techniques. High conductivity contribution in dielectric loss does not allow the study of the segmental a relaxation associated with the glass transition. In the glassy state two secondary relaxation mechanisms have been investigated, the gamma and the beta mechanism. The gamma relaxation mechanism, at low temperatures/high frequencies, is attributed to motions of the end groups (-OH for polyurethanes and -NH2 for polyureas), and has been found faster in the hyperbranched polyureas. in addition, our results reveal that gamma relaxation mechanism in both series depends on the chemical structure, being faster for aliphatic structures. The beta relaxation mechanism, at higher temperatures/lower frequencies, is attributed to the motions of branched ends with polar groups. Our study suggests that this mechanism may be a typical relaxation process for hyperbranched polyurethanes structures, not existed in the linear counterparts. All the systems exhibit dc conductivity at temperatures higher than T-g which shows Arrhenius-like temperature dependence and is characterized by rather high activation energies (in the order of 200 kJ/mol). At temperatures lower than T-g all the systems studied exhibit remarkably high charge mobility. In particular, aliphatic hyperbranched polyureas exhibit dc conductivity which has been found to be of VTF type concerning the temperature dependence. This result implies that the conduction mechanism is coupled with molecular motions in the glassy state of the polymer. (C) 2009 Elsevier Ltd. All rights reserved.	en
heal.publisher	ELSEVIER SCI LTD	en
heal.journalName	Polymer	en
dc.identifier.doi	10.1016/j.polymer.2009.06.037	en
dc.identifier.isi	ISI:000268732500021	en
dc.identifier.volume	50	en
dc.identifier.issue	16	en
dc.identifier.spage	4039	en
dc.identifier.epage	4047	en