a) b - École Polytechnique de Montréal

2.1.2.1 Binary Polymer Blends
2.1.2.1.1 Co-continuous Morphology
There is currently an increasing interest in techniques used to control interfacial properties of
polymeric materials. Through controlling morphology of polymer blends, novel materials for
different applications can be designed. For immiscible polymer binary blends, two types of
morphologies, namely matrix/dispersed structure and co-continuous morphologies, have been
realized. At low concentration of one phase, dispersed droplets of that phase in the other
component is observed. By increasing the concentration of the minor phase, phase inversion
occurs and a dual phase region is reached in which various levels of co-continuous structure coexist.
At concentrations near the phase inversion region, blends with two fully interconnected
and interpenetrating structures in three dimensions are observed. In other words, a binary blend
is formed of two polymers in which the surface of each phase is an exact topological replica of
the other (antitropic). Generally, in polymer blends, the matrix dominates the properties of blend;
thus, in binary co-continuous blends both polymers have approximately equal contributions to
the blend properties. Moreover, their interpenetrating assembly can lead to synergistic
improvement of specific conductivity, permeability, and mechanical properties. A process in
which two phases switch their functions is defined as phase inversion. In a certain concentration
range around the phase inversion concentration, which is defined as the co-continuity interval,
co-continuous morphologies are formed. The phase inversion concentration is regarded as the
center of this area and its correct determination is of great importance in which the former
dispersed phase becomes the matrix and vice-versa. Consequently, the position and width of the
phase inversion concentration are influenced by many rheophysical material parameters of the
blend’s constituents, such as interfacial tension. Willemse et al.(Willemse, Posthuma de Boer,
van Dam, & Gotsis, 1999) showed that for different blends with various matrix viscosities and
viscosity ratios, the composition range within which fully co-continuous polymer blend
structures form is influenced by interfacial tension. It was found(He, Bu, & Zeng, 1997) that
phase co-continuity occurs in a wide composition range at a short mixing time, but with
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