Related Experiment Video
Updated: Aug 9, 2025
11:44
Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
Published on: October 18, 2018
26.6K
Analysis of Poly(thiourethane) Covalent Adaptable Network through Broadband Dielectric Spectroscopy.
B Pascual-Jose1, S De la Flor2, A Serra3
1Institute of Technology of Materials (ITM), Universitat Politècnica de València (UPV), Camí de Vera, s/n, 46022València, Spain.
ACS Applied Polymer Materials
|February 23, 2023
Summary
Dielectric analysis of poly(thiourethane) networks reveals six distinct processes. The study identifies noncooperative local motions and a dissociative molecular exchange mechanism in HDI-S3.
Area of Science:
- Polymer Science
- Dielectric Spectroscopy
- Materials Chemistry
Background:
- Poly(thiourethane) networks are advanced materials with complex dielectric behaviors.
- Understanding dielectric processes is crucial for predicting material performance and stability.
- HDI-S3 is a specific poly(thiourethane) network requiring detailed characterization.
Purpose of the Study:
- To analyze the dielectric spectra of the HDI-S3 poly(thiourethane) network.
- To determine the nature and cooperativity of six observed dielectric processes.
- To elucidate the molecular mechanisms underlying these relaxations, including the glass transition and bond exchange reactions.
Main Methods:
- Dielectric spectroscopy was employed to analyze the poly(thiourethane) network.
- Analysis of dielectric spectra across various temperatures to identify relaxation processes.
- DC conductivity (σDC) measurements were used to investigate the bond exchange reaction.
Main Results:
- Six dielectric processes were identified: γ1, γ2, β (noncooperative local motions), αTg (glass transition), α* (bond exchange), and ρ (heterogeneity).
- Apparent activation energies for low-temperature relaxations were determined (30, 36, 60 kJ·mol−1).
- The α* relaxation is linked to a dissociative bond exchange mechanism, supported by DC conductivity analysis.
Conclusions:
- The HDI-S3 network exhibits complex dielectric behavior with both local motions and cooperative processes.
- A dissociative molecular exchange mechanism governs the α* relaxation, indicating dynamic chemical changes within the network.
- Further investigation is needed to confirm the origin of the ρ relaxation attributed to sample heterogeneity.
Related Concept Videos
01:32UV–Vis Spectroscopy of Conjugated Systems
7.2K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent...
One of the factors influencing λmax is the extent...
7.2K
01:26Susceptibility, Permittivity and Dielectric Constant
1.7K
When placed in an external electric field, a dielectric material gets polarized. The charge density in the dielectric material is given by the sum of the bound and free charge densities, while the total charge density can also be written in terms of the total electric field. The bound charge density can be measured in terms of polarization, leading to the relationship between electric displacement and polarization.
1.7K
01:29UV–Vis Spectroscopy: Woodward–Fieser Rules
24.9K
UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a given...
24.9K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
1.6K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
1.6K