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Atomistic simulations of spinodal phase separation preceding polymer crystallization
Richard H Gee1, Naida Lacevic, Laurence E Fried
1University of California, Lawrence Livermore National Laboratory, Chemistry and Materials Science Directorate, Livermore 94551, USA. gee10@llnl.gov
Nature Materials
|December 29, 2005
Summary
Polymer melts exhibit a precrystallization phase characterized by density fluctuations and ordered domains. This study reveals a coexistence period where nucleation, growth, and phase separation mechanisms interact before full crystallization.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Polymer crystallization is a critical process in material properties.
- Previous studies focused on nucleation and growth mechanisms.
- The precrystallization (induction) period involves pretransition states and phase separation.
Purpose of the Study:
- To investigate the early ordering stages in polymer melts before crystallization.
- To understand the mechanisms occurring during the induction period.
- To explore the relationship between polymer chain rigidity and ordering.
Main Methods:
- Large-scale computer simulations of polymer melts.
- Analysis of density and orientational fluctuations.
- Identification of ordered domains and phase behavior.
Main Results:
- Identified growing dense regions similar to smectic liquid crystals in ordered domains.
- Revealed a 'coexistence period' preceding crystallization.
- Observed the interplay of nucleation, growth, and phase separation mechanisms during ordering.
Conclusions:
- Polymer ordering before crystallization involves complex mechanisms beyond simple nucleation and growth.
- Phase separation plays a significant role in the early stages of polymer ordering.
- Simulations provide insights into the isotropic-to-nematic transition and its link to chain rigidity.