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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
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Pressure-Induced Polymerization of LiN(CN)2
Derek W Keefer, Huiyang Gou1,2, Andrew P Purdy3
1Geophysical Laboratory, Carnegie Institution of Washington , 5251 Broad Branch Road NW, Washington, DC, 20015, United States.
The Journal of Physical Chemistry. A
|October 30, 2016
Summary
High pressure transforms lithium dicyanamide (LiN(CN)2) into a polymerized network. This novel material, featuring sp2-hybridized bonds, is recoverable but sensitive to air and moisture.
Area of Science:
- Materials Science
- High-Pressure Physics
- Solid-State Chemistry
Background:
- Lithium dicyanamide (LiN(CN)2) is a compound with potential applications.
- Understanding its behavior under extreme conditions is crucial for materials development.
Purpose of the Study:
- To investigate the high-pressure phase transformations of lithium dicyanamide.
- To characterize the structural and vibrational properties of its high-pressure phases.
Main Methods:
- In situ Raman and infrared (IR) spectroscopies.
- Synchrotron angle-dispersive powder X-ray diffraction (PXRD).
- Diamond anvil cell (DAC) up to 22 GPa.
- Density functional perturbation theory calculations.
Main Results:
- A polymorphic phase transformation was observed around 8 GPa.
- Above 18 GPa, polymerization of dicyanamide units forms a disordered network.
- The polymerized product exhibits sp2-hybridized carbon-nitrogen bonds and a visible absorption edge near 540 nm.
Conclusions:
- Lithium dicyanamide undergoes significant structural changes under high pressure, including polymerization.
- The polymerized product is recoverable to ambient conditions but is unstable in air/moisture.
- The study provides insights into the pressure-induced evolution of nitrogen-carbon compounds.
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