Multifunctional Block Copolymer: Where Polymetallic
and Polyelectrolyte Blocks Meet
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Abstract
Sequential
reversible addition–fragmentation transfer (RAFT)
polymerization of a mixed sandwich cobaltocene monomer (η<sup>5</sup>-cyclopentadienyl-cobalt-η<sup>4</sup>-cyclobutadiene
(CpCoCb)) and a phosphonium salt functionalized styrene monomer resulted
in the first example of a unique multifunctional block copolymer consisting
of a metallopolymer block and a polyelectrolyte block. The polyelectrolyte
block was decorated with a gold anion (AuCl<sub>4</sub><sup>–</sup>) via salt metathesis, resulting in a heterobimetallic block copolymer
with distinct gold and cobalt sections. Solution self-assembly behavior
of this unique metallopolymer-<i>b</i>-polyelectrolyte copolymer
before and after salt metathesis was studied. Heterobimetallic micelles
with a gold containing core and a cobalt-containing corona were obtained,
and then the core was reduced to form gold nanoparticles (AuNPs).
Studies on the solid-state self-assembly of this unique block copolymer
showed that it phase separated into hexagonally packed cylinders.
Salt metathesis of the phase-separated block copolymers was utilized
as the first example of a nonstandard selective staining method to
exclusively stain the polyelectrolyte domains with the AuCl<sub>4</sub><sup>–</sup> anion. Staining the metallopolymer domain by
RuO<sub>4</sub> provided the complementary pattern. Pyrolysis of the
self-assembled block copolymers resulted in magnetic cobalt-phosphate
nanoparticles with 17% char yield