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Updated: Jun 6, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
High-pressure vibrational properties of polyethylene
Luca Fontana1, Mario Santoro, Roberto Bini
1LENS, European Laboratory for Non-Linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino (FI), Italy.
Polyethylene remains stable up to 50 GPa, exhibiting distinct phase transitions with significant hysteresis. A comprehensive phase diagram reveals its behavior under extreme pressure and temperature conditions.
Area of Science:
- Materials Science
- Solid-State Physics
- Polymer Science
Background:
- Understanding the high-pressure behavior of polymers like polyethylene is crucial for materials science.
- Polyethylene's structural phase transitions under pressure are not fully characterized.
- Investigating intermolecular interactions provides insight into material properties.
Purpose of the Study:
- To investigate the pressure-induced vibrational spectral changes in polyethylene up to 50 GPa.
- To identify and characterize phase transitions and their associated hysteresis.
- To construct a phase diagram and analyze intermolecular interactions.
Main Methods:
- Fourier-transform infrared (FTIR) spectroscopy.
- Raman spectroscopy.
- Density-functional theory (DFT) calculations at 0 K.
Main Results:
- Detected orthorhombic Pnam to monoclinic P2(1)/m phase transition with significant hysteresis.
- Observed pronounced hysteresis for the higher-pressure transition to the monoclinic A2/m phase.
- Confirmed structural and chemical stability of polyethylene up to 50 GPa after compression/decompression cycles.
Conclusions:
- Polyethylene exhibits complex phase transitions under high pressure, marked by substantial hysteresis.
- A phase diagram for polyethylene up to 50 GPa and 650 K was proposed.
- Analysis of spectral changes provides insights into intermolecular forces in crystalline polyethylene.
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