Complexity of Polymer Phase Transitions

Soft matter is often called complex fluids. Polymers are one type of complex fluids. Their complex behaviors in phase transitions appear in the spatial and temporal evolution of multi-phase structures. Often, multiple phase transitions coexist and interplay with each other, either in cooperation or in competition. Therefore, the subject of complex systems may be helpful in our elucidation of the complex formation mechanism of multi-phase structures. 

The interplay of polymer phase transitions has been extensively studied in solutions, dated back to Richards in 1946 (Richards 1946). Flory s classical book in 1953 introduced the complete set of phase diagrams (Flory 1953). Recently, Cheng comprehensively reviewed the experimental progress on the interplay of polymer phase transitions (Cheng 2008). Keller emphasized in a review paper that, in the preparation of the thermoreversible gel, crystallization can freeze the gel structure generated by the prior continuous phase separation (Keller 1995). A practical example of such interplay of phase transitions is in the production of 

11 Interplay Between Phase Separation and Polymer Crystallization 

Polymer phase separation and crystallization, as introduced separately in the previous two chapters, have different molecular driving forces that can be simultaneously expressed by the use of the lattice model. Adjusting the corresponding driving forces, the mean-field theory can predict the phase diagrams, and at the meanwhile molecular simulations can demonstrate the complex phase transition behaviors of polymers in the multi-component miscible systems. 

The interplay of phase separation and polymer crystallization in the multi-component systems influences not only the thermodynamics of phase transitions, but also their kinetics. This provides an opportunity to tune the complex morphology of multi-phase structures via the interplay. In the following, we further introduce three aspects of theoretical and simulation progresses enhanced phase separation in the blends containing crystallizable polymers accelerated crystal nucleation separately in the bulk phase of concentrated solutions, at interfaces of immiscible blends and of solutions, and in single-chain systems and interplay in diblock copolymers. In the end, we introduce the implication of interplay in understanding biological systems. 

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