The role of metastable states
in polymer phase transitions
报告人：
University of Akron, USA
程正迪教授
时间： 5月25日上午9:00-11:30, 下午1:00-3:30
地点：东华大学松江校区2号学院楼516室
时间： 5月26日上午9:00-11:30, 下午1:00-3:30
5月28日下午1:00-4:00
地点：东华大学松江校区图文中心第二报告厅
欢迎本校及兄弟院校感兴趣的师生参加
纤维材料改性国家重点实验室
材料科学与工程学院
2007.5.18
Abstract
Classical metastable states possess a local free energy minimum at infinite sizes, but not a global free energy minimum. This concept is phase size independent. We have studied a number of experimental results and propose a new concept – that there exists a wide range of metastable states in polymers where their metastability is critically determined by the phase size and dimensionality. We call this multi-length scale type of phase behavior morphological metastability. This concept successfully explains the experimental observation of phase stability inversion that is solely determined by phase sizes.
Metastable states are also observed in phase transformations that are kinetically impeded on the pathway to thermodynamic equilibrium. This has been illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification and gel formation, as well as combinations of these transformation processes. In these cases, the metastable state often becomes the dominant state for the entire system, and is observed over a range of size and time scales.
