Use of Dielectric Spectroscopy To Monitor Molecular Mobility in Glassy and Supercooled Trehalose

Bhardwaj, Sunny P.; Suryanarayanan, Raj

doi:10.1021/jp303317p

Cited by 18 publications

(23 citation statements)

References 57 publications

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“…Several different approaches have been used in order to reveal the existence of small intensity processes compared to the conductive signal, in the dielectric loss spectrum [17,18,19,20,21]. One of them, is based on the use of the alternative representation, in terms of the dielectric modulus, which can be evaluated from the permittivity as M* ( ω ) = 1/ ε* ( ω ).…”

Section: Resultsmentioning

confidence: 99%

Molecular Dynamics of Functional Azide-Containing Acrylic Films

et al. 2018

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A report on the syntheses, thermal, mechanical and dielectric characterizations of two novel polymeric acrylic materials with azide groups in their pendant structures is presented. Having the same general structure, these polymers differ in length of oxyethylene units in the pendant chain [-CONH-CH2CH2-(O-CH2CH2)nN3], where n is 1 (poly(N-(2-(2-azidoethoxy)ethyl)methacrylamide), PAzMa1) or 2 (poly(N-2-(2-(2-azidoethoxy)ethoxy)ethyl)methacrylamide), PAzMa2), leading with changes in their dynamics. As the thermal decomposition of the azide group is observed above 100 °C, dielectric analysis was carried out in the temperature range of −120 °C to 100 °C. Dielectric spectra of both polymers exhibit in the glassy state two relaxations labelled in increasing order of temperature as γ- and β-processes, respectively. At high temperatures and low frequencies, the spectra are dominated by ohmic conductivity and interfacial polarization effects. Both, dipolar and conductive processes were characterized by using different models. Comparison of the dielectric activity obtained for PAzMa1 and PAzMa2 with those reported for crosslinked poly(2-ethoxyethylmethacrylate) (CEOEMA) was performed. The analysis of the length of oxyethylene pendant chain and the effect of the methacrylate or methacrylamide nature on the dynamic mobility was analysed.

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Section: Resultsmentioning

confidence: 99%

Molecular Dynamics of Functional Azide-Containing Acrylic Films

et al. 2018

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“…reported for small molecules [27] but never in polymer materials with practical applications and with a unique experimental tech nique. Studies coupling BDS and thermally stimulated depolariza tion currents (TSDC) reported that the a mode evolved from a VFT dependence at higher frequencies (BDS in the rubbery state) to an Arrhenius dependence at lower frequencies (TSDC in the glassy state) [28].…”

Section: Molecular Mobility Associated With the Glass Transition In Ementioning

confidence: 99%

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 2. electrochemical impedance spectroscopy study

Roggero

Caussé

Dantras

et al. 2019

Electrochimica Acta

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In this series, an epoxy varnish for the corrosion protection of carbon steel was analysed in the dry state by broadband dielectric spectroscopy (part 1) to describe the molecular mobility of the epoxy network. Electrochemical impedance spectroscopy (EIS) measurements were then performed in a NaCl solution (part 2), with the intent to detect the signature of the molecular mobility in the wet state. The dielectric manifestation of the glass transition (a mode), previously characterized in part 1 of this series for the dry varnish, was evidenced from EIS measurements through the use of the dielectric permittivity formalism. This a mode showed the characteristic Vogel Fulcher Tamman dependence, shifted towards higher frequencies when compared to that of the dry varnish, consistently with the plasticization of the epoxy network due to the water uptake. Moreover, it was shown that taking the a mode into account when fitting the EIS impedance data with equivalent circuits led to a much better fit in the capacitive resistive transition region. It was shown that the dc charge transport processes are not only triggered but also governed by the molecular mobility of the epoxy network. In the case of thick coatings (several hundreds of micrometers), this dependence demonstrated the absence of through pores, as it is often discussed in the literature. Indeed, under the assumption of current flowing through free electrolyte via open pores, the temperature dependence of the electrolyte's dc conductivity (Arrhenius law) should be found instead of the temperature dependence of molecular mobility.

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“…Therefore, mechanistic investigation of reduced crystallization tendency due to restricted molecular mobility of amorphous drugs in PASD is essential to assess their stability. DSC, 122 solid-state nuclear magnetic resonance (ssNMR), 123 and dielectric spectroscopy 124 are commonly used to monitor molecular mobility in glass systems.…”

Section: Reduction Of Molecular Mobility Of Amorphous Drug In Pasdmentioning

confidence: 99%

Polymeric Amorphous Solid Dispersions: A Review of Amorphization, Crystallization, Stabilization, Solid-State Characterization, and Aqueous Solubilization of Biopharmaceutical Classification System Class II Drugs

Baghel

Cathcart

O’Reilly

2016

Journal of Pharmaceutical Sciences

786

452

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Poor water solubility of many drugs has emerged as one of the major challenges in the pharmaceutical world. Polymer-based amorphous solid dispersions have been considered as the major advancement in overcoming limited aqueous solubility and oral absorption issues. The principle drawback of this approach is that they can lack necessary stability and revert to the crystalline form on storage. Significant upfront development is, therefore, required to generate stable amorphous formulations. A thorough understanding of the processes occurring at a molecular level is imperative for the rational design of amorphous solid dispersion products. This review attempts to address the critical molecular and thermodynamic aspects governing the physicochemical properties of such systems. A brief introduction to Biopharmaceutical Classification System, solid dispersions, glass transition, and solubility advantage of amorphous drugs is provided. The objective of this review is to weigh the current understanding of solid dispersion chemistry and to critically review the theoretical, technical, and molecular aspects of solid dispersions (amorphization and crystallization) and potential advantage of polymers (stabilization and solubilization) as inert, hydrophilic, pharmaceutical carrier matrices. In addition, different preformulation tools for the rational selection of polymers, state-of-the-art techniques for preparation and characterization of polymeric amorphous solid dispersions, and drug supersaturation in gastric media are also discussed.

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Use of Dielectric Spectroscopy To Monitor Molecular Mobility in Glassy and Supercooled Trehalose

Cited by 18 publications

References 57 publications

Molecular Dynamics of Functional Azide-Containing Acrylic Films

Molecular Dynamics of Functional Azide-Containing Acrylic Films

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 2. electrochemical impedance spectroscopy study

Polymeric Amorphous Solid Dispersions: A Review of Amorphization, Crystallization, Stabilization, Solid-State Characterization, and Aqueous Solubilization of Biopharmaceutical Classification System Class II Drugs

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