Star Polymer Unimicelles on Graphene Oxide Flakes
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Abstract
We report the interfacial assembly
of amphiphilic heteroarm star
copolymers (PS<sub><i>n</i></sub>P2VP<sub><i>n</i></sub> and PS<sub><i>n</i></sub>(P2VP-<i>b</i>-P<i>t</i>BA)<sub><i>n</i></sub> (<i>n</i> = 28 arms)) on graphene oxide flakes at the air–water interface.
Adsorption, spreading, and ordering of star polymer micelles on the
surface of the basal plane and edge of monolayer graphene oxide sheets
were investigated on a Langmuir trough. This interface-mediated assembly
resulted in micelle-decorated graphene oxide sheets with uniform spacing
and organized morphology. We found that the surface activity of solvated
graphene oxide sheets enables star polymer surfactants to subsequently
adsorb on the presuspended graphene oxide sheets, thereby producing
a bilayer complex. The positively charged heterocyclic pyridine-containing
star polymers exhibited strong affinity onto the basal plane and edge
of graphene oxide, leading to a well-organized and long-range ordered
discrete micelle assembly. The preferred binding can be related to
the increased conformational entropy due to the reduction of interarm
repulsion. The extent of coverage was tuned by controlling assembly
parameters such as concentration and solvent polarity. The polymer
micelles on the basal plane remained incompressible under lateral
compression in contrast to ones on the water surface due to strongly
repulsive confined arms on the polar surface of graphene oxide and
a preventive barrier in the form of the sheet edges. The densely packed
biphasic tile-like morphology was evident, suggesting the high interfacial
stability and mechanically stiff nature of graphene oxide sheets decorated
with star polymer micelles. This noncovalent assembly represents a
facile route for the control and fabrication of graphene oxide-inclusive
ultrathin hybrid films applicable for layered nanocomposites