Phase behavior and molecular mobility in polyurethane/styrene–acrylonitrile blends

Vatalis, A. S.; Kanapitsas, A.; Delides, C. G.; Viras, Kyriakos; Pissis, P.

doi:10.1002/app.1192

Cited by 11 publications

(13 citation statements)

References 36 publications

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“…It is well established that, because of the similar range of the equivalent frequency of TSDC and of DSC measurements of about 10 À2 -10 À4 Hz, 30,33 the TSDC a peak is in the temperature region of calorimetric T g . 34 For pure Jeffamine D2000 the TSDC a peak is at about À75 C (inset to Fig. 2), in agreement with the results of DSC measurements (not shown here).…”

Section: Resultssupporting

confidence: 90%

“…This coincidence, observed also in previous work, 34,53 is an important fact from the methodological and the metrological point of view, as it allows to practically extend the frequency range of dielectric measurements down to low frequencies not easily accessible by DRS.…”

Section: Figuresupporting

confidence: 63%

“…T a , the temperature of current maximum, is a good measure of the calorimetric T g . 30,34 DT 1/2 is the difference between the two temperatures where the depolarization current becomes half of the current maximum. It provides a measure for the distribution of relaxation times contributing to the TSDC peak.…”

Section: Resultsmentioning

confidence: 99%

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Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Kourkoutsaki

Logakis

Kroutilová

et al. 2009

J of Applied Polymer Sci

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Dielectric techniques, including thermally stimulated depolarization currents (TSDC, À150 to 30 C) and, mainly, broadband dielectric relaxation spectroscopy (DRS, 10 À2 -10 6 Hz, À150 to 150 C) were employed, next to differential scanning calorimetry (DSC), to investigate molecular dynamics in rubbery epoxy networks prepared from diglycidyl ether of Bisphenol A (DGEBA) and poly (oxypropylene)diamine (Jeffamine D2000, molecular mass 2000) and modified with polyhedral oligomeric silsesquioxanes (POSS) units covalently bound to the chains as dangling blocks. Four relaxations were detected and analyzed: in the order of increasing temperature at constant frequency, two local, secondary c and b relaxations in the glassy state, the segmental a relaxation associated with the glass transition and the normal mode relaxation, related with the presence of a dipole moment component along the Jeffamine chain contour. Measurements on pure Jeffamine D2000 helped to clarify the molecular origin of the relaxations observed. A significant reduction of the magnitude and a slight acceleration of the a and of the normal mode relaxations were observed in the modified networks. These results suggest that a fraction of polymer is immobilized, probably at interfaces with POSS, due to constraints imposed by the covalently bound rigid nanoparticles, whereas the rest exhibits a slightly faster dynamics due to increaseof free volume resulting from loosened molecular packing of the chains (plasticization by the bulky POSS units).The increase of free volume is rationalized by density measurements.

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Section: Resultssupporting

confidence: 90%

Section: Figuresupporting

confidence: 63%

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Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Kourkoutsaki

Logakis

Kroutilová

et al. 2009

J of Applied Polymer Sci

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“…DSC measurements on the salt form of the t‐AIPNs under investigation here indicated, in agreement with the results reported here, that the α relaxation of CPU becomes slightly slower in the IPNs; however, these results were not confirmed by DMA 21. The composition dependence of the characteristics of the α and of the MWS relaxation of the CPU component can be discussed in terms of modification of both the DMS28 and of crystallinity of CPU in the t‐AIPNs. Inherent to this discussion is the assumption (simplification) that the relaxations of the CPU component are not affected by the presence of the copolymer component in the t‐AIPNs.…”

Section: Resultssupporting

confidence: 87%

Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid block copolymer: Structure–property relationships

Kanapitsas

Lebedev

Slisenko

et al. 2006

J of Applied Polymer Sci

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Thermoplastic apparent interpenetrating polymer networks (t-AIPNs) of crystallizable polyurethane (CPU) and a styrene/acrylic acid block copolymer (S-b-AA, acid form) of several compositions were prepared by casting from a common solvent. A variety of experimental techniques, including size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), broadband dielectric relaxation spectroscopy (DRS), thermally stimulated depolarization currents (TSDC), and density measurements were employed to investigate structureproperty relationships of the t-AIPNs. Special attention was paid to the investigation of molecular dynamics of the CPU component in the t-AIPNs, by combination of the dielectric DRS and TSDC techniques, as well as from the methodological point of view, to the prospects of morphological characterization by broadband DRS. The results show that the CPU/S-b-AA t-AIPNs studied can be considered as multiphase systems having at least two amorphous and one crystalline phases, as well as regions of mixed compositions. Their properties are determined by the heterogeneity of the individual components, as well as by the heterogeneity caused by the thermodynamic incompatibility of these components. The degree of incompatibility is determined, to a large extent, by the intermolecular hydrogen bonding between the functional groups of the CPU and the S-b-AA components (ester groups and COOH-groups, respectively), which is more effective on addition of small amounts of either of the components.

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“…Georgoussis et al [21] and Vatalis et al [29] have also discussed the occurrence of a TSDC current peak in polyurethane around this temperature region. The presence of unsaturated butadiene and carbonyl groups is mainly responsible for the charge trapping in LCPU.…”

Section: Low-temperature Tsdc Studies Of Lcpumentioning

confidence: 95%

Low-Temperature TSDC Studies of Molecular Dynamics in Pristine and O⁷⁺Ion–Modified Liquid Crystalline Polyurethane

Lal

Quamara

2014

International Journal of Polymer Analysis and Characterization

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The molecular dynamics of pristine and 100 MeV O 7þ ion-modified liquid crystalline polyurethane (LCPU) was carried out using the thermally stimulated depolarization currents (TSDC) method. The TSDC spectra of pristine LCPU samples consist of current peaks appearing around 110,160, 210, and 260 K and are called the c, b, a, and d peaks respectively. The c-peak is attributed to the crankshaft motion of the spacer group (but-2-ene group). The b-peak is due to the localized rotational fluctuations of C=O groups. The a-peak is associated with the dipolar orientation of imines group present in the urethane linkage, and the d-peak has its origin in the space charge trapping mechanism. In the TSDC spectra of O 7þ ion-irradiated LCPU samples the c-peak almost disappears, which shows that the ion induced modification in the methylene linkage. A relaxation process owing to new sub-polar groups formed due to dehydrogenation of CH 2 groups and occurring in the vicinity of b-relaxation is discussed. The radiation-induced chain scissioning at NH groups in LCPU is also confirmed from the fluence effect on the a-peak. The irradiation results in the production of a large number of defect sites and an increase in the same results in the enhancement of d-relaxation.

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Phase behavior and molecular mobility in polyurethane/styrene–acrylonitrile blends

Cited by 11 publications

References 36 publications

Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid block copolymer: Structure–property relationships

Low-Temperature TSDC Studies of Molecular Dynamics in Pristine and O⁷⁺Ion–Modified Liquid Crystalline Polyurethane

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Phase behavior and molecular mobility in polyurethane/styrene–acrylonitrile blends

Cited by 11 publications

References 36 publications

Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Polymer dynamics in rubbery epoxy networks/polyhedral oligomeric silsesquioxanes nanocomposites

Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid block copolymer: Structure–property relationships

Low-Temperature TSDC Studies of Molecular Dynamics in Pristine and O7+Ion–Modified Liquid Crystalline Polyurethane

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Low-Temperature TSDC Studies of Molecular Dynamics in Pristine and O⁷⁺Ion–Modified Liquid Crystalline Polyurethane