Broadband Dielectric Spectroscopy Studies of Hyperbranched Polyglycerols

Garcı́a-Bernabé, Abel; Díaz‐Calleja, Ricardo; Haag, Rainer

doi:10.1002/macp.200600025

Cited by 16 publications

(19 citation statements)

References 35 publications

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“…In the same way as for PEI2000 [ 69 ], the β- and γ-relaxations of the PEI800 and PEI25000 are independent of the α-relaxation; in particular, the β-relaxation does not present the appearance of a Johari-Goldstein (JG) relaxation, according to its common classification [ 82 ], in contrast to what is observed for the pure epoxy resin [ 69 ]. For some other hyperbranched polymers, such as polyglycerols [ 83 ] and polyester amides [ 84 ], the β-relaxation presents JG behaviour, whereas in others, for example, polyesters [ 80 ], it does not.…”

Section: Resultsmentioning

confidence: 99%

Study of Hyperbranched Poly(ethyleneimine) Polymers of Different Molecular Weight and Their Interaction with Epoxy Resin

2018

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Two different commercial hyperbranched poly(ethyleneimine)s (HBPEI), with molecular weights (MW) of 800 and 25,000 g/mol, and denoted as PEI800 and PEI25000, respectively, as well as the mixtures with a Diglycidyl Ether of Bisphenol-A (DGEBA) epoxy resin, have been studied using thermal analysis techniques (DSC, TGA), dielectric relaxation spectroscopy (DRS), and dynamic mechanical analysis (DMA). Only a single glass transition is observed in these mixtures by DSC. DRS of the HBPEIs shows three dipolar relaxations: γ, β, and α. The average activation energy for the γ-relaxation is similar for all HBPEIs and is associated with the motion of the terminal groups. The β-relaxation has the same average activation energy for both PEI800 and PEI25000; this relaxation is attributed to the mobility of the branches. The α-relaxation peak for all the HBPEIs is an asymmetric peak with a shoulder on the high temperature side. This shoulder suggests the existence of ionic charge trapped in the PEI. For the mixtures, the γ- and β-relaxations follow the behaviour of the epoxy resin alone, indicating that the epoxy resin dominates the molecular mobility. The α-relaxation by DRS is observed only as a shoulder, as a consequence of an overlap with conductivity effects, whereas by DMA, it is a clear peak.

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Section: Resultsmentioning

confidence: 99%

Study of Hyperbranched Poly(ethyleneimine) Polymers of Different Molecular Weight and Their Interaction with Epoxy Resin

2018

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“…The β- and γ-relaxations are independent from the α-relaxation; in particular, the β-relaxation does not present the appearance of a Johari-Goldstein (JG) relaxation, according to its common classification [ 83 ], in contrast to what is observed for the pure epoxy resin, as is shown immediately below. For some other hyperbranched polymers, such as polyglycerols [ 57 ] and polyester amides [ 84 ], the β-relaxation presents a Johari-Goldstein behaviour, whereas in others, for example polyesters [ 60 ], it does not.…”

Section: Resultsmentioning

confidence: 99%

“…The molecular dynamics of a wide variety of dendrimers [ 51 , 52 , 53 , 54 ] and, in particular, HBPs, including hyperbranched polyurethanes [ 55 , 56 ], polyglycerols [ 57 , 58 ], polyesters [ 59 , 60 , 61 ], and polyamide systems [ 62 , 63 ], have been studied by dielectric spectroscopy. In most cases, these dendrimers and HBPs display a glass transition and two secondary relaxations, the γ-relaxation invariably being attributed to motion of the terminal groups.…”

Section: Introductionmentioning

confidence: 99%

Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix

2016

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The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: HBPEI, epoxy and an epoxy/HBPEI mixture, denoted ELP. The DRS behaviour is monitored in the ELP system in three stages: prior to curing, during curing, and in the fully cured system. In the stage prior to curing, DRS measurements show three dipolar relaxations: γ, β and α, for all systems (HBPEI, epoxy and ELP). The α-relaxation for the ELP system deviates significantly from that for HBPEI, but superposes on that for the epoxy resin. The fully cured thermoset displays both β- and α-relaxations. In DMA measurements, both α- and β-relaxations are observed in all systems and in both the uncured and fully cured systems, similar to the behaviour identified by DRS.

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“…22 Deconvolutions of the overlapping peaks in the loss spectra were carried out by fitting Havriliak-Negami ͑HN͒ type equations 23 to the experimental loss isotherms or loss spectra. 22 Deconvolutions of the overlapping peaks in the loss spectra were carried out by fitting Havriliak-Negami ͑HN͒ type equations 23 to the experimental loss isotherms or loss spectra.…”

Section: Introductionmentioning

confidence: 99%

Secondary and primary relaxations in hyperbranched polyglycerol: A comparative study in the frequency and time domains

Garcı́a-Bernabé

Dominguez-Espinosa

Díaz‐Calleja

et al. 2007

The Journal of Chemical Physics

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The non-Debye relaxation behavior of hyperbranched polyglycerol was investigated by broadband dielectric spectroscopy. A thorough study of the relaxations was carried out paying special attention to truncation effects on deconvolutions of overlapping processes. Hyperbranched polyglycerol exhibits two relaxations in the glassy state named in increasing order of frequency beta and gamma processes. The study of the evolution of these two fast processes with temperature in the time retardation spectra shows that the beta absorption is swallowed by the alpha in the glass-liquid transition, the gamma absorption being the only relaxation that remains operative in the liquid state. In heating, a temperature is reached at which the alpha absorption vanishes appearing the alphagamma relaxation. Two characteristics of alpha absorptions, decrease of the dielectric strength with increasing temperature and rather high activation energy, are displayed by the alphagamma process. Williams' ansatz seems to hold for these topologically complex macromolecules.

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Broadband Dielectric Spectroscopy Studies of Hyperbranched Polyglycerols

Cited by 16 publications

References 35 publications

Study of Hyperbranched Poly(ethyleneimine) Polymers of Different Molecular Weight and Their Interaction with Epoxy Resin

Study of Hyperbranched Poly(ethyleneimine) Polymers of Different Molecular Weight and Their Interaction with Epoxy Resin

Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix

Secondary and primary relaxations in hyperbranched polyglycerol: A comparative study in the frequency and time domains

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