Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates

Area of Science:

• Rheology
• Molecular Dynamics
• Machine Learning

Background:

• Understanding the molecular-scale rheological properties of liquids and polymers is crucial for applications like lubrication and hydraulic fracking.
• Squalane exhibits significant shear thinning at high strain rates and pressures.

Purpose of the Study:

• To investigate the correlation between rheological properties and molecular structure of squalane under shear.
• To analyze changes in molecular orientation during shear thinning using machine learning.

Main Methods:

• Nonequilibrium molecular dynamics simulations.
• Principal Component Analysis (PCA) and t-distributed Stochastic Neighbor Embedding (t-SNE) for dimension reduction and visualization.
• Analysis of intramolecular and intermolecular atom pair orientation tensors.

Main Results:

• At low pressures, strain rate strongly correlates with intramolecular orientation changes.
• At high pressures, molecular orientation is primarily classified by atom pair types, not strain rate.
• No clear link was found between high-pressure shear thinning and intermolecular orientation changes.

Conclusions:

• Intramolecular orientation evolution is limited at high pressures.
• Squalane molecule alignment saturates during high-pressure shear thinning.
• Machine learning effectively visualizes molecular orientation changes during shear thinning.