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Spin–Spin Coupling: One-Bond Coupling

Spin–Spin Coupling: One-Bond Coupling

Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...

NMR Spectroscopy: Spin–Spin Coupling

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...

Spin–Spin Coupling Constant: Overview

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...

Sources and Properties of Electric Charge

Sources and Properties of Electric Charge

All objects we see around us consist of atoms, which combine to form molecules. The lightest element in the universe is hydrogen, and a hydrogen atom consists of a positively charged proton and a negatively charged electron. The magnitude of charge that a proton and an electron carry are the same, and it is the fundamental unit of charge. In SI units, it is 1.602 times 10-19 coulomb.
Most atoms additionally constitute another fundamental particle, the neutron. It carries no electrical charge. A...

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Updated: Feb 15, 2026

The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

Published on: June 7, 2020

Coupling Mechanical and Electrical Properties in Spin Crossover Polymer Composites.

Sylvain Rat¹, Mario Piedrahita-Bello¹, Lionel Salmon¹

¹LCC, CNRS & University of Toulouse (UPS, INPT), 205 route de Narbonne, 31077, Toulouse, France.

Advanced Materials (Deerfield Beach, Fla.)

|January 10, 2018

Summary

This study integrates spin crossover nanoparticles into flexible polymers, creating novel materials with tunable electromechanical properties for applications in artificial muscles and thermal energy harvesting.

Keywords:

electromechanical effects molecular switches polymer composites spin-crossover

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The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

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Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

Published on: September 19, 2020

Area of Science:

Materials Science
Nanotechnology
Polymer Science

Background:

Spin crossover (SCO) materials exhibit unique responses to external stimuli.
Integrating SCO nanoparticles into polymer matrices can lead to novel composite properties.

Purpose of the Study:

To develop flexible nanocomposite materials by dispersing SCO nanoparticles in polymer matrices.
To investigate the electromechanical coupling and potential applications of these SCO-polymer composites.

Main Methods:

Homogeneous dispersion of [Fe{(Htrz)2(trz)}0.9(NH2-trz)0.3](BF4)1.1 nanoparticles (20 nm ± 8 nm) in P(VDF-TrFE) and PVDF matrices.
Fabrication of macroscopic, freestanding, and flexible nanocomposite films.
Characterization of thermal, mechanical, dielectric, and piezoelectric properties, including poling of P(VDF-TrFE) samples.

Main Results:

The nanocomposites exhibit concomitant thermal expansion and discharge current peaks around SCO transition temperatures.
Poling P(VDF-TrFE) composites resulted in a piezoelectric coefficient (d33) of -3.3 pC N-1.
Significant changes in strain (1%) and permittivity (40%) were observed during the SCO transition, indicating strong electromechanical coupling.

Conclusions:

The synergistic interaction between SCO nanoparticles and polymer matrices creates novel "product properties."
These SCO-polymer nanocomposites show promise for applications as actuators in artificial muscles and generators for thermal energy harvesting.