a) b - École Polytechnique de Montréal

of PANI, and an increase in the conductivity of the sample, as for this blend conductivity reaches
a relatively high value of 0.017 S/cm.
a) b) c)
Figure A-4.1. Scanning electron micrographs of HDPE/PVDF/PANI after extraction of PVDF by
DMF (a) 33/33/33, (b) 40/20/40, and (c) 45/10/45
The approach obtained for HDPE/PVDF/PANI can be used to decrease the percolation
threshold of PANI in a HDPE/PEMA/PANI blend. In such a conversion, HDPE plays a major
role as it forms a continuous structure containing large rods and branches, and consequently
limiting the space, whereas PANI can generate clusters only in limited routes. In this part, two
ternary blends of HDPE/PEMA/PANI and PS/PEMA/PANI are studied from electrical and
morphological points of view. It is shown that the high surface tension of HDPE and PANI
results in a positive spreading coefficient: λPEMA/PANI = 8 mN/m in HDPE/PEMA/PANI,
according to the Harkins equation (interfacial tensions are listed in Table A-4.1). Therefore,
PEMA locates at the interface of HDPE and PANI, separating them. In such a morphology, due
to high interfacial tension between HDPE and PEMA, large continuous parts of HDPE exist in
the blend, which restricts the area for diffusion of PANI. Therefore, connected pathways of
PANI are achieved at a lower amount of PANI, leading to a decrease in the percolation threshold
of PANI, and subsequently increasing the value of conductivity. In the ternary PS/PEMA/PANI,
due to a positive spreading coefficient of λPEMA/PANI = 3.2 mN/m, the PEMA phase is located at
the interface of the PS and PANI phases (Table A-4.1). Contrary to the previous case, with a low
amount of PANI, the percolation threshold is not reached due to the low interfacial tension of PS
and PEMA, resulting in PANI droplets remaining in the blend.
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