Related Experiment Video
Updated: Aug 28, 2025
10:35
Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
8.8K
Domain-Specific Phase Transitions in a Supramolecular Nanostructure.
Samuel J Kaser1, Ty Christoff-Tempesta2, Linnaea D Uliassi2
1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts02139, United States.
Journal of the American Chemical Society
|September 20, 2022
Summary
This study reveals distinct thermal phase behaviors in different domains of supramolecular aramid amphiphile (AA) nanoribbons. Electron paramagnetic resonance (EPR) spectroscopy identified unique dynamics and phase transitions, crucial for designing advanced nanomaterials.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Understanding thermal phase behavior in nanomaterials is key for applications in medicine and energy.
- Supramolecular nanostructures offer tunable properties but require detailed characterization.
Purpose of the Study:
- To resolve the thermal phase behavior of discrete domains within a supramolecular aramid amphiphile (AA) nanoribbon.
- To characterize the distinct conformational dynamics and phase transitions at different sites within the nanoribbon.
Main Methods:
- Utilized X-band Electron Paramagnetic Resonance (EPR) spectroscopy with site-specific spin labels.
- Analyzed electron paramagnetic resonance (EPR) line shapes to determine conformational dynamics.
- Measured conformational mobility as a function of temperature to identify phase transitions.
Main Results:
- Distinct conformational dynamics were observed, with fastest mobility at the surface water layer, intermediate in the head group domain, and slowest in the interior aramid domain.
- First- and second-order phase transitions were identified, including melting in surface and head group domains.
- A temperature-insensitive crystalline phase was found in the aramid domain, with distinct activation energies of diffusion determined via Arrhenius analysis.
Conclusions:
- Electron paramagnetic resonance (EPR) spectroscopy can resolve distinct thermal phase behaviors between adjacent nanodomains.
- This characterization is vital for the rational design of supramolecular nanostructures for various technological applications.
- The findings highlight the utility of EPR for detailed thermal phase characterization of complex nanostructures.
Related Concept Videos
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
1.7K
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...
1.7K
02:39Phase Transitions: Melting and Freezing
12.6K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
12.6K
02:31Phase Transitions
19.6K
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to...
19.6K
01:58Cooperative Allosteric Transitions
8.0K
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
8.0K
03:02Colors and Magnetism
12.3K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
12.3K
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
1.1K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.1K