Star block copolymer electrolytes
with a lithium-ion conducting
phase are investigated in the present work to assess the influence
of this complex architecture compared to that of the linear one, on
both, bulk morphology and ionic conductivity. For that purpose, the
controlled synthesis of a series of poly(styrene-co-benzyl methacrylate)-b-poly[oligo(ethylene glycol)
methyl ether acrylate] [P(S-co-BzMA)-b-POEGA] block copolymers (BCPs) by reversible addition–fragmentation
transfer polymerization was performed from either a monofunctional
or a tetrafunctional chain transfer agent containing trithiocarbonate
groups. We emphasized how a small amount of styrene (6 mol %) drastically
improved the control of the RAFT polymerization of benzyl methacrylate
mediated by the tetrafunctional chain transfer agent. Transmission
electron microscopy and small-angle X-ray scattering demonstrated
a clear segregation of the BCPs in the presence of lithium salt. Interestingly,
the star BCPs gave rise to highly ordered lamellar structures as compared
to that of the linear analogues. Consequently, the reduced lamellae
tortuosity of self-assembled star BCPs improved the lithium conductivity
by more than 8 times at 30 °C for ∼30 wt % of the POEGA
conductive phase.