There
is a challenge to achieve the maximum feasible charge transport
property for conductive polymer nanocomposites containing graphitic
nanoparticles. Multi-walled carbon nanotube (MWCNT) and graphene hybridization
is a commonly investigated solution for enhancing the electron conduction
in these nanocomposites. In this work, we present the functionalized
octopus-shaped hybrid of MWCNT/graphene (FOS-hybrid), where the nanotube
ends and graphene edges are stitched together by ethylenediamine and
are subsequently functionalized by octadecylamine (ODA). At the identical
total weight percentages of nanoparticles, the poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS)-based nanocomposites of the FOS-hybrid demonstrate
superior electrical conductivity, σdc, compared to
SEBS-based nanocomposites of ODA-functionalized MWCNT or graphene
and even their physically incorporated hybrid. The synergistic ratio
equal to the ratio of “σdc of the hybrid nanoparticles
composite” to “σdc of the single nanofiller
composite” with higher σdc is approximately
15.6 for the FOS-hybrid. This obtained synergistic ratio is the highest
reported value for hybrid systems comprising MWCNT and graphene so
far. In contrast to the majority of previous investigations, the improvement
in the dispersion state is not the main reason for synergism in this
work, and the observed remarkable synergism is attributed to the extremely
structured networks of octopus-shaped particles with low tunneling
resistivity at MWCNT/graphene junctions. The Monte Carlo simulation
shows that the significant “average number of active neighboring
particles” for the conducting network of FOS-hybrid is what
makes their network very efficient, which is not just originated from
the expected complexity imposed by hybridization. Additionally, the
SEBS-based nanocomposite with 5 wt % FOS-hybrid particles displays
high elongation at break (765%) and low electromechanical sensitivity
(ΔR/R
0 = 0.52 at
100% strain). This result is attributed to the superb dispersion affected
by ODA-functionalization and covalent bonding between hybrid components
in octopus-shaped particles, which does not break under strain. Therefore,
strain-insensitive stretchable conductors can be produced by FOS-hybrid
nanocomposites.