Dielectric Study of Frozen Aqueous Solutions of Ionic Materials by Means of Thermally Stimulated Depolarization Currents

Laudat, J.; Laudát, F.

doi:10.1524/zpch.1991.174.part_2.211

Cited by 9 publications

(1 citation statement)

References 14 publications

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“…Following the established terminology, the water content can be categorized in bulk, loosely bound, and tightly bound fractions. These fractions relax at different temperature ranges of the TSDC spectrum . Thus, the progressive high-temperature shift and weakening of the TSD current signal (Figure , plots b, c, and d) reflect the gradual desorption of water molecules.…”

Section: Resultsmentioning

confidence: 94%

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics

Kalogeras

Vassilikou‐Dova

2001

J. Phys. Chem. B

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Modifications in the molecular dynamics of the side-chain relaxation in poly(methyl methacrylate) (PMMA) have been recorded by monitoring the thermally stimulated depolarization currents (TSDC) β-relaxation band of PMMA in three systems: bulk PMMA, PMMA polymerized in situ in porous SiO2, and lasing matrixes with rhodamine 6G/Cl- (R6G) and a perylene derivative (PG). To study the different types of inter- and intramolecular interactions, a range of dye concentrations and different polymerization initiators have been tested. In PMMA + SiO2, the low-temperature (LT) shift of the β-band and the increase of the energy barriers (W) associated with the side-chain (re)orientation are attributed to various counterbalancing effects. A scheme of extensive hydrogen-bond interactions (surface or chemical effect) between the ester carbonyls of PMMA and the silicic acid pore surface is used to explain the overall increase in the distributed energy barriers. In contrast, the reduction of the polymer's chain entanglements and the increase in the free volume (structural or physical effect), due to the pore-directed polymerization, are considered to loosen up several steric hindrances on the rotational motion. The modification of the relaxation times spectrum prompts the shift of the β-relaxation in PMMA + SiO2. In R6G + PMMA, the drastic LT shift of the β-band indicates the partial coupling between the chromophores and the side-group rotations. The TSDC spectrum does not present a rotational relaxation of the polar rhodamine dye. In R6G + PMMA + SiO2, the presence of the chromophores on the pore surfaces and the corresponding decrease of the “effective” average pore diameters available for MMA diffusion and PMMA growth balance the physical and chemical effects, as depicted in the similarity of the energy distributions. The speedup of the β-relaxation with increasing dye content is ascribed to the reduced exposure of the side groups to chemical effects. The positive energy shift in PG + PMMA + SiO2 can be explained by considering the mixing of PG and PMMA, which permits strong hydrogen-bonding interactions and simultaneously reduces PMMA's free volume. TSDC signals around room temperature (RT) are tentatively discussed in terms of a Maxwell−Wagner−Sillars (MWS) polarization mode at the PMMA−SiO2 interface.

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Section: Resultsmentioning

confidence: 94%

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics

Kalogeras

Vassilikou‐Dova

2001

J. Phys. Chem. B

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Dielectric study of charge motion in DNA

Laudat

Laudát

1992

Eur Biophys J

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Abstract. The d.c. conductivity and daelectric properties of solid low-humidity NaDNA layers have been examined over frequency and temperature ranges up to 105 Hz and 80-330 K respectively. The results presented are basically consistent with a model in which the majority charge carriers are protons (H30 +, OH-) moving on the surface of a NaDNA chain in the neighbourhood of the phosphate groups. The increasing hydration also increases the mobility of counterions (Na +) and their contribution to a d. c. conductivity. The Arrhenius d. c. conductivity seems to be limited by electrochemical processes on the electrodes. Low-frequency dispersion is also caused by this effect. The local and long-range motion of charge carriers is limited below temperatures of a dipolar thermally stimulated depolarization current (TSDC) peak observed in the range 165-255 K. The amplitude and position of the peak depend strongly on the water content in the sample.

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Dynamic properties of water in porous Vycor glass studied by dielectric techniques

Pissis

Laudat

Daoukaki

et al. 1994

Journal of Non-Crystalline Solids

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Dielectric Study of Frozen Aqueous Solutions of Ionic Materials by Means of Thermally Stimulated Depolarization Currents

Cited by 9 publications

References 14 publications

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics

Dielectric study of charge motion in DNA

Dynamic properties of water in porous Vycor glass studied by dielectric techniques

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Dielectric Study of Frozen Aqueous Solutions of Ionic Materials by Means of Thermally Stimulated Depolarization Currents

Cited by 9 publications

References 14 publications

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO2 Matrixes Doped with Luminescent Organics

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO2 Matrixes Doped with Luminescent Organics

Dielectric study of charge motion in DNA

Dynamic properties of water in porous Vycor glass studied by dielectric techniques

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Product

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Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics

Dielectric Probe of Intermolecular Interactions in Poly(methyl methacrylate) (PMMA) and PMMA + SiO₂ Matrixes Doped with Luminescent Organics