a) b - École Polytechnique de Montréal

2.1.2.2.2 Double-Percolated Systems
Zhang et al.(J. Zhang, et al., 2007) showed that through a combination of composite droplet and
co-continuous blend morphology preparation methodologies, a continuous shell structure of one
component was situated at the interface of a co-continuous structure of two other phases. In a
composite-droplet structure with composite droplets of PMMA in PS, if the amount of HDPE is
decreased while the quantity of the PMMA is increased, a co-continuous network of HDPE and
PMMA is formed while the PS forms a continuous sheath structure at the HPDE/PMMA
interface (Figure 2-7a). In this kind of morphology, it is possible to have a co-continuous
structure of one component using a very small amount of that component. The percolation
threshold is significantly decreased and continuity development increases as compared to
classical blends. This is verified by gravimetric measurement, as shown in Figure 2-7b. As it is
illustrated, the percolation threshold of the PS phase in a HDPE/PS blend and that of the PMMA
phase in a HDPE/PMMA blend are 15% and 20%, respectively. The percolation threshold of PS
sharply decreases when it is situated at the interface of HDPE and PMMA, whereas at
concentrations as low as 3%, 70% continuity is observed.
a) b) c)
Figure 2-7. a, b) FIB-AFM images of HDPE/PS/PMMA ternary blends. The white line in Figure
7b indicates the section analyzed below, and c) Continuity of PS or PMMA as a function of the
composition using the solvent dissolution technique(Zhang, et al., 2007)
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