Evaluation of activation parameters of molecular mobility of parylene C using differential scanning calorimetry, dielectric spectroscopy, and thermally stimulated depolarization currents.
The molecular kinetics of α-relaxation were studied by dielectric spectroscopy (DS) and thermally stimulated depolarization currents (TSDC) for the thermoplastic semicrystalline parylene C (-H2C-C6H3Cl-CH2-)n thin film. Activation energy of the α-relaxation process brings very close values with both methods (155 ± 2 kJ mol(-1)). Dielectric spectroscopy carried out in a wide temperature range allowed one to determine the α-relaxation time against the temperature and then to estimate the Kauzmann and Angell temperatures for parylene C. From these temperatures and the determination of kinetics and thermodynamics parameters from DSC analysis, it was possible to investigate the cooperative rearranging region (CRR) in parylene C. CRR is quantified in terms of characteristic length (ζCRR), volume (VCRR), number z of rearranging units, and height barrier Δμ of the rearranging unit. Moreover, the fragility index m, calculated from these three methods, is discussed. A value of m = 94 is obtained by DSC confirming a "strong" character of parylene C. A lowest value of 35 ± 4 obtained from electric analyses (DS and TSDC) must be considered with caution because these methods of characterizations bring into play only dipolar relaxations. Last, the kinetic and thermodynamic parameters for parylene C highlighted in this work are positioned in comparison with other organic and inorganic materials.
Grenoble Electrical Engineering Laboratory (G2ELab), Joseph Fourier University (UJF), CNRS , 25 Rue des Martyrs, BP 166, 38042 Grenoble Cedex 9, France.
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Kahouli
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Sylvestre
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Jomni
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Yangui