Miscibility Criterion in Polymer Blends and its Determination

This chapter reviews the main techniques for the assessment of blend miscibility. The phase behavior of polymers differs considerably from that of small molecules, whether in solution or in mixtures with other polymers. The development of any polymer blend system, including selection and performance, crucially depends on our ability to predict and control phase behavior as well as blend morphology. To achieve this, understanding of the parameters that govern polymer-polymer miscibility is vital. Thermodynamics offers an unambiguous way to predict whether a binary mixture is miscible or immiscible and provides a quantitative determination of the polymer-polymer interaction energies. This is important since the interaction between polymer-polymer pairs affects the physical and mechanical properties of miscible systems and, for immiscible ones, it determines the nature and the width of the interface between the two polymers. The determination of polymer-polymer miscibility is a very important aspect of blending.