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Interplay between two phase transitions: crystallization and liquid-liquid phase separation in a polyolefin blend.
Xiaohua Zhang1, Zhigang Wang, Xia Dong
1Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Science and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, CAS, Beijing 100080, China.
The Journal of Chemical Physics
|July 20, 2006
Summary
Liquid-liquid phase separation (LLPS) in polymer blends significantly impacts crystallization kinetics. A new "fluctuation assisted nucleation" mechanism explains how LLPS concentration fluctuations enhance crystal nucleation rates.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Liquid-liquid phase separation (LLPS) is a phenomenon influencing polymer blend properties.
- Crystallization kinetics are critical for determining material performance.
- Understanding the interplay between LLPS and crystallization is essential for designing advanced polymer materials.
Purpose of the Study:
- To investigate the relationship between liquid-liquid phase separation (LLPS) and crystallization in statistical copolymer blends.
- To elucidate the mechanism by which LLPS affects crystallization kinetics.
- To propose and validate a novel nucleation mechanism.
Main Methods:
- Optical Microscopy (OM) for visualizing phase morphology.
- Atomic Force Microscopy (AFM) for surface characterization.
- Differential Scanning Calorimetry (DSC) for analyzing thermal transitions and crystallization kinetics.
Main Results:
- Deep quenching of polymer blends induced interconnected bicontinuous structures characteristic of spinodal decomposition via LLPS.
- A subsequent quench below the melting point revealed a significant alteration in crystallization kinetics.
- The observed changes in crystallization were attributed to an increased nucleation rate, driven by concentration fluctuations from spinodal LLPS.
Conclusions:
- A novel mechanism, termed "fluctuation assisted nucleation," is proposed for crystallization in interactive blend systems exhibiting LLPS.
- Experimental evidence from OM, AFM, and DSC supports the proposed fluctuation assisted nucleation model.
- This study provides new insights into the complex interplay between phase separation and crystallization in polymer blends.