ABSTRACT
Knowledge of phase behavior (thermodynamics) of polymer solutions is important for the design of many processes and products, including many specific applications in colloid and surface chemistry.
Among the many applications, we can mention:
1. Design of separations for the removal of unreacted monomers, colorants, by-products, and additives after solution or emulsion polymerizations [1]
2. Selection of appropriate mixed solvents for paints and coatings, which can meet strict production and environmental criteria (fewer VOCs, water based) [2,3]
3. Numerous applications in the coatings industry, for example, in the control of emissions during production and application, the effect of temperature, and swelling of film or sorption of gases and chemicals from the atmosphere [3-6]
4. Novel recycling methods for polymer waste based on physicochemical methods, the so-called selective dissolution [7,8]
[9] or novel structures, for example, star or hyberbranched polymers [10,11]
6. Permeabilities of gases in the flexible polymeric pipelines used, for example, in the North Sea for transporting hydrocarbons from the seabed to the surface [12,13]
7. Use of CO2 as user-friendly solvent for many polymer-related applications including those involving paints and coatings [14-16]
8. Simultaneous representation of bulk and surface thermodynamic properties [17] 9. Migration of plasticizers from poly(vinyl chloride) (PVC) [18-21] 10. Separation of proteins based on the so-called aqueous two-phase systems using polymers like PEG or Dextran
[1,22,23] 11. Choice of suitable solvents for polymers and especially copolymers used as stabilizers in colloidal dispersions
The above list shows some of the many applications where polymer thermodynamics plays a key role. Polymer solutions and blends are complex systems: frequent existence of liquid-liquid equilibria (upper critical solution temperature [UCST], lower critical solution temperature [LCST], closed loop, etc.), the significant effect of temperature and polymer molecular weight (Mw), including polydispersity in phase equilibria, free-volume (FV) effects, and other factors may cause difficulties. For this reason, many different models have been developed for polymer systems and often the situation may seem rather confusing to the practicing engineer.
