Phase Transitions in Polymers: The Role of Metastable States

Phase transition play a central role in connecting the field of structural analysis and dynamics in changes. This book attempts to utilize the concepts of metastable states and metastability to link these two research fields and illuminate the physics beind polymeric phase transitions. A classical metastable state possesses a local free energy minimum at infinite size but not a global one, This concept is phase size independent. We now know that two types of metastable states can be identified. The first type is associated with the supercooling or superheating of a phase before a phase transition has time to occur, while the second type is associated with competing kinetic pathways caused by the existence of multiple free energy paths to reach the equilibrium phase. We have studied a number of experimental results and proposed that there are a wide range of metastable states in polymers at different length and time scales. The effect of phase size on metastability is specifically introduced and discussed. Metastable states can be identified by structural and morphological investigations of crystallization along with mesophase transitions, liquid-liquid phase separation, vitrification and gel formation, as well as combinations of these transformation processes. The phase behavior of polymers is thus dominated by the interdependence of metastable states at different length and time scales.…