Dielectric spectroscopy of the characterization of the structure of amorphous polymeric materials

Bernès, A.; Chatain, D.; Fauran-Clavel, M.J.; Lacabanne, C.; Ibar, J. P.

doi:10.1109/icpadm.1988.38504

Cited by 3 publications

(10 citation statements)

References 12 publications

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“…There is a linear relationship between log 10 (τ 0 ) and E a that can be appreciated in figure 6. This relationship is known as compensation law [3]. The concordance between the WP and NIW linear regression parameters is very accurate.…”

Section: Analysis Of Tsdc Datamentioning

confidence: 96%

“…The relative weight of each contribution, g, is roughly proportional to the polarization of the peak which, at its turn, is proportional to its area. To take into account the dependence of polarizability with temperature, the area is multiplied by T p to obtain g [3]. Figure 5 shows the relative distribution of weights for the α relaxation, calculated in this way.…”

Section: Analysis Of Tsdc Datamentioning

confidence: 99%

“…TSDC has shown greater sensitivity in studying the glass transition of polymers. The most interesting feature of TSDC is its ability to study in its own each mode of a distributed process [3], as discussed below. Although TSDC is able to provide the relaxation time of each mode, it does not give information about the geometry of the reorientation processes, as, for example, multidimensional NMR [4], or the spatial heterogeneity of the relaxation, as, for example, nonresonant spectral hole burning [5].…”

Section: Introductionmentioning

confidence: 99%

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TSDC study of the glass transition: correlation with calorimetric data

Diego¹,

Sellarès²,

Aragoneses³

et al. 2007

J. Phys. D: Appl. Phys.

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The glass transition in amorphous poly(ethylene terephthalate) is studied by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The ability of TSDC to decompose a distributed relaxation, as the glass transition, into its elementary components is demonstrated. Two polarization techniques, windows polarization (WP) and non-isothermal windows polarization (NIW), are employed to assess the influence of thermal history in the results. The Tool-Narayanaswami-Moynihan (TNM) model has been used to fit the TSDC spectra. The most important contributions to the relaxation comes from modes with non-linearity (x) around 0.7. Activation energies yield by this model are located around 1 eV for polarization temperature (T p ) below 50 • C and they raise up to values higher than 8 eV as T p increases (up to 80 • C). There are few differences between results obtained with WP and NIW but, nonetheless, these are discussed. The obtained kinetic parameters are tested against DSC results in several conditions. Calculated DSC curves at several cooling and heating rates can reproduce qualitatively experimental DSC results. These results also demonstrate that modelization of the non-equilibrium kinetics involved in TSDC spectroscopy is a useful experimental tool for glass transition studies in polar polymers.

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Section: Analysis Of Tsdc Datamentioning

confidence: 96%

Section: Analysis Of Tsdc Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

TSDC study of the glass transition: correlation with calorimetric data

Diego¹,

Sellarès²,

Aragoneses³

et al. 2007

J. Phys. D: Appl. Phys.

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show abstract

“…Further information relative to the glass transition can be obtained performing a RMA [15]. In fact, one of the main advantages of the TSDC technique is that it allows one to study on its own the parts of the mechanism (modes) that give rise to the relaxation as a whole [16].…”

Section: Relaxation Map Analysismentioning

confidence: 99%

“…The most interesting feature of TSDC is the ability to resolve a complex relaxation into its elementary components. This is done using a procedure known as relaxation map analysis (RMA) [15]. If the polarizing field, in a TSDC experiment, is on during a large portion of the cooling ramp (conventional polarization) many relaxation processes can be detected in the same thermogram.…”

Section: Introductionmentioning

confidence: 99%

A study of the glass transition in the amorphous interlamellar phase of highly crystallized poly(ethylene terephthalate)

Sellarès¹,

Diego²,

Belana³

2010

J. Phys. D: Appl. Phys.

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Poly(ethylene terephthalate) (PET) is a semi-crystalline polymer that can be crystallized up to different degrees heating from the amorphous state. Even when primary crystallization has been completed, secondary crystallization can take place with further annealing and modify the characteristics of the amorphous interlamellar phase. In this work we study the glass transition of highly crystallized PET and in which way it is modified by secondary crystallization. Amorphous PET samples were annealed for 4 hours at temperatures between 140 • C and 180 • C. The secondary crystallization process was monitored by differential scanning calorimetry and the glass transition of the remaining interlamelar amorphous phase was studied by Thermally Stimulated Depolarization Currents measurements. Non-isothermal window polarization is employed to resolve the relaxation in modes with a well-defined relaxation time that are subsequently adjusted to several standard models. Analysis of experimental results reveal that cooperativity is so diminished in crystallized samples with respect to the amorphous material that it can be neglected in the modellization of data. The evolution of the modes during secondary crystallization, once primary crystallization has been completed, gives more weight to lower energy modes. As a consequence, secondary crystallization tends to lower the glass transition temperature of the amorphous interlamellar phase, although remaining noticeably higher than in amorphous samples. Evolution of calorimetric scans of the glass transition are simulated from the obtained results and show the same behavior. It can be concluded that primary and secondary crystallization act in opposite directions on the glass transition temperature of the material even though the effect of secondary crystallization is much slighter. The interpretation of these results in terms of current views about secondary crystallization is discussed.

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Comparative dielectric and thermally stimulated-depolarization-current studies of the liquid crystal dimers 1″,9″-bis(4-cyanobiphenyl-4′-yl) nonane and heptane and a binary mixture between them, close to the glass transition

et al. 2022

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We have performed dielectric spectroscopy and thermally stimulated-depolarization-current experiments to study the molecular dynamics of the twist-bend nematic phase close to the glass transition of two members of the 1 ,7 -bis(4-cyanobiphenyl-4 -yl)alkane homologous series (CBnCB): the liquid crystal (LC) dimers CB9CB and CB7CB, as well as a binary mixture of both. By doping CB9CB with a small quantity of CB7CB, the crystallization is inhibited when cooling the sample down, while the bulk properties of CB9CB are retained and we can investigate the supercooled behavior close to the glass transition. The study reveals that the inter-and intramolecular interactions of the mixture are similar to those of pure CB9CB and confirms that there is a single glass transition in symmetric LC dimers.

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Dielectric spectroscopy of the characterization of the structure of amorphous polymeric materials

Cited by 3 publications

References 12 publications

TSDC study of the glass transition: correlation with calorimetric data

TSDC study of the glass transition: correlation with calorimetric data

A study of the glass transition in the amorphous interlamellar phase of highly crystallized poly(ethylene terephthalate)

Comparative dielectric and thermally stimulated-depolarization-current studies of the liquid crystal dimers 1″,9″-bis(4-cyanobiphenyl-4′-yl) nonane and heptane and a binary mixture between them, close to the glass transition

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