Broadband dielectric spectroscopy of the inter- and intramolecular dynamics of a series of random polyester copolymers

Merenga, A. S.; Papadakis, C. M.; Kremer, F.; Liu, J.; Yee, Albert F.

doi:10.1007/s003960100509

Cited by 12 publications

(12 citation statements)

References 15 publications

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“…It is known that the β-relaxation of PCT is closely related with segmental motions of cyclohexylene rings undergoing the chair-tochair conformational transition. 11,13,15,27 However, unlike other poly(alkylene terephthalate)s such as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), 1,2,24,28-32 the dynamic mechanical properties of PHT associated with segmental motions have not been investigated extensively. 1 It was reported that the dynamic mechanical spectra of poly(alkylene terephthalate)s have the same pattern exhibiting two main α-and β-relaxation processes, except for the fact that both relaxation peaks shift to lower temperature with increasing the number of methylene groups in poly (alkylene terephthalate)s. 1 The α-and β-relaxation processes of poly(alkylene terephthalate)s are ascribed to the glass transition and the sub-glassy segmental motions, respectively.…”

Section: Resultsmentioning

confidence: 99%

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Jeong

Lee

2006

Macromol. Res.

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The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan δ versus temperature: the primary α-relaxation associated with the glass transition and the secondary β-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both α-and β-relaxation temperatures increased with increasing CT content. The activation energy of the α-relaxation increased with increasing CT content, whereas that of the β-relaxation decreased. The sub-glassy secondary β-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.

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Section: Resultsmentioning

confidence: 99%

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Jeong

Lee

2006

Macromol. Res.

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“…34 Kremer, et al incorporated cyclohexylene rings into the main-chains of PET and reported a cooperative secondary relaxation of ester group interactions with "chair-chair" conformational transitions. 35 Yee and coworkers reported the secondary relaxation in BPA-PC was associated with cooperative motions of chain lengths up to seven repeat units. 36 In contrast, BPA-polyformals containing methylene-diether groups represent more flexible polymers and show no evidence of cooperation larger than one repeat unit.…”

Section: Secondary Relaxationsmentioning

confidence: 99%

Improving the Distortional Deformation Capabilities of Aerospace Composite Networks

Wiggins¹

2011

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Standard Form 298 (Rev. 8/98) REPORT DOCUMENTATION PAGE Prescribed by ANSI Std. Z39.18Form The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

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“…17 The situation is different in random copolymers where a single glass temperature is commonly anticipated. Indeed, many random copolymers were investigated with differential scanning calorimetry (DSC), 18−31 rheology, 18−20,26,30−32 dielectric spectroscopy (DS), 24,27,33,34 ellipsometry, 35,36 molecular dynamics simulations, 33 and theory. 37 There is now a vast literature on the composition dependence of glass temperature in such systems.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Heterogeneity in Random Copolymers of Polymethacrylates Bearing Different Polyhedral Oligomeric Silsesquioxane Moieties (POSS)

et al. 2017

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Random copolymersusually considered as dynamically homogeneous with a single glass temperaturecan show dynamic heterogeneity by appropriate choice of their repeat units. Random copolymers based on polymethacrylates with polyhedral oligomeric silsesquioxane (POSS) moieties as side groups substituted with seven isobutyl ((i-Bu)7POSS-OSiMe2(CH2)3-MA) and 2,4,4-trimethylpentyl ((i-C8H17)7POSS-OSiMe2(CH2)3-MA) groups were synthesized and studied by dielectric spectroscopy, density functional theory, differential scanning calorimetry, and rheology. Two distinct relaxation processes were found by dielectric spectroscopy giving rise to two glass temperatures. In addition, rheology revealed significant broadening of the viscoelastic functions leading eventually to the failure of time–temperature superposition for all copolymer compositions. These results provide signatures of dynamic heterogeneity in a random copolymer.

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Broadband dielectric spectroscopy of the inter- and intramolecular dynamics of a series of random polyester copolymers

Cited by 12 publications

References 15 publications

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Improving the Distortional Deformation Capabilities of Aerospace Composite Networks

Dynamic Heterogeneity in Random Copolymers of Polymethacrylates Bearing Different Polyhedral Oligomeric Silsesquioxane Moieties (POSS)

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