a) b - École Polytechnique de Montréal

In the case where PS is the matrix, the value of interfacial energy results in a
(PMMA+PP/HDPE) structure, in which HDPE is encapsulated by PP and PMMA is separately
dispersed in the matrix (Figure 2-13b). For PMMA and HDPE matrices, structures of
(PS/PP/HDPE) (Figure 2-13c) and (PP/PS/PMMA) (Figure 2-13d) were predicted and observed,
respectively.
2.1.3 Porous Polymeric Substrates Prepared by Melt-Blending
Highly controlled polymeric co-continuous structures have been fabricated in our group(J. Li &
Favis, 2001b; Jianming Li, Ma, & Favis, 2002; Sarazin & Favis, 2003) through a melt-blending
process of immiscible polymers followed by selective solvent extraction. As mentioned before,
in a binary immiscible polymer blend, two possible morphologies can be formed: dispersed
droplet/matrix and co-continuous morphologies. Binary polymer blends comprised of polymer 1
and polymer 2 in the co-continuity range lead to a co-continuous morphology at concentrations
above the percolation threshold. The dual phase region is located at concentrations above the
percolation threshold, where phase inversion determines the area that two fully interconnected
phases through a continuous pathway exist. Etching one of the components by selective solvent
extraction leads to a fully interconnected porous substrate. The greatest advantage of this method
compared to other techniques used for generating interconnected porous polymer substrates, such
as solvent casting/particulate leaching or gas foaming, is the ability to control porosity and pore
distribution, and internal surface area.
2.1.3.1 Controlling the Pore Size in the Substrate
There are a few ways to control the pore sizes of porous samples prepared via melt-blending.
Pore size and extent of continuity can be controlled through composition, interfacial
modification, and static annealing. Interfacial modification in a blend is employed to achieve
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