a) b - École Polytechnique de Montréal

where the number of segments of the two polymers are represented by M1 and M2, and Vs is the
volume of the segments(Scott, 1949).
2.1.2 Immiscible Polymer Blends
Most polymer blends are immiscible, showing phase-separated mixture. Morphology of
multiphase polymer blend materials can be controlled by controlling the interfacial chemistry
and the microstructure. Three parameters determine the properties of these multiphase materials:
properties of the component polymers, interaction and adhesion between phases and
morphology(Utracki, 1998). The properties of multiphase materials are strongly dependent on
their phase morphology. Controlling parameters on morphology of polymer blends include
composition of phases, kinematic or rheological properties (elasticity and viscosity), processing
conditions (shear stress, processing temperature,…), and the most important one which is a
thermodynamic parameter: the interfacial tension of the pair of phases(Favis, 2000; Steinmann,
Gronski, & Friedrich, 2001). Thermodynamics of interfaces defines the interfacial tension
between two phases as the area derivative of the surface free energy per unit area of an interface.
Equation 2-11.
Equation 2-12.
⎛ G ⎞
⎜
∂
γ ⎟
ij = and
⎜ A ⎟
⎝ ∂ ij ⎠
⎛ F ⎞
⎜
∂
γ ⎟
ij =
⎜ A ⎟
⎝ ∂ ij ⎠
T , P,
n
T , V , n
where G is the Gibbs free energy, F is the Helmholtz free energy of the whole system, and Aij is
the interfacial area between phases i and j.
There are different ways to measure interfacial tension of two polymers, including theoretical
methods such as Antonoff’s rule(Antonoff, 1942; Antonoff, 1907), the Good and Girifalco
equation(Girifalco & Good, 1957; Good & Girifalco, 1964), and harmonic mean equation, and
experimental methods such as the breaking thread, pendant drop, and sessile drop methods.
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