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Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend
Hua Jiang1, Nannan Dou, Guoqiang Fan
1Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China.
The Journal of Chemical Physics
|October 5, 2013
Summary
In binary polymer blends, stationary in-plane thermal gradients accelerate phase separation via spinodal decomposition. This occurs by enhancing concentration fluctuations both above and below the spinodal line, even inducing it in one-phase regions.
Area of Science:
- Materials Science
- Polymer Science
- Physical Chemistry
Background:
- Phase separation in binary polymer blends is crucial for material properties.
- Spinodal decomposition is a key mechanism driving this process.
- Understanding the influence of external fields like thermal gradients is essential.
Purpose of the Study:
- To investigate structure formation during spinodal decomposition in binary polymer blends under in-plane thermal gradients.
- To determine the effect of thermal gradients on phase separation kinetics and mechanisms.
- To explore phase separation behavior above and below the spinodal line.
Main Methods:
- Experimental investigation using phase contrast optical microscopy.
- Utilizing a temperature gradient hot stage for in-plane stationary thermal gradients.
- Annealing experiments under homogeneous and gradient temperature conditions.
Main Results:
- Phase-separated domains grow faster under thermal gradient annealing compared to homogeneous conditions.
- A coupling between concentration fluctuations and thermal gradients was observed below the spinodal line.
- In-plane thermal gradients induce phase separation even in the one-phase regime above the spinodal line.
Conclusions:
- In-plane thermal gradients significantly accelerate spinodal decomposition in binary polymer blends.
- Enhanced concentration fluctuations are the primary mechanism for accelerated phase separation.
- Stationary thermal gradients can alter equilibrium phase diagrams and induce phase separation in systems with an upper critical solution temperature.
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