Pressure induced polymerization of fluid ethylene

Area of Science:

• Polymer Chemistry
• Materials Science
• Physical Chemistry

Background:

• Ethylene polymerization is crucial for polymer production.
• Understanding polymerization under extreme conditions is scientifically significant.
• High pressure and temperature can alter polymerization pathways and polymer properties.

Purpose of the Study:

• To investigate the spontaneous polymerization of fluid ethylene under high temperature and pressure.
• To determine the reaction kinetics and activation energy.
• To elucidate the reaction mechanism and characterize the resulting polymer structure.

Main Methods:

• Fourier Transform Infrared (FTIR) absorption spectroscopy for in-situ characterization.
• Resistively heated membrane diamond anvil cell for high pressure (0.4-1.5 GPa) and temperature (340-423 K) experiments.
• FTIR, Raman spectroscopy, and X-ray diffraction for post-reaction polymer analysis.

Main Results:

• The instability boundary for spontaneous polymerization was identified.
• Reaction kinetics were measured at 1.5 GPa and temperatures from 340 to 423 K.
• High-quality crystalline polymers were recovered and characterized.

Conclusions:

• The activation energy and initiation step molecularity offer insights into the polymerization mechanism.
• The growth of polymer in hot fluid monomer likely contributes to the high crystallinity.
• This study provides a fundamental understanding of ethylene polymerization under extreme conditions.