The
use of the traditional growing-from approach to prepare surface-initiated
polymer brushes is widespread as it produces polymer brushes with
higher grafting densities than grafting-to methods. In this article,
we present an investigation of a passing-though approach that supplies
the monomer from below the initiator-functionalized surface, inverting
the concentration gradient found in the traditional growing-from technique
that has been shown to increase the D̵ of brushes.
Using Fourier transform infrared (FTIR) spectroscopy mapping combined
with substrate masking, we show that the brushes incorporate only
monomer diffusing from below and not from the surrounding solution.
Further, we characterize these brushes with contact angle analysis,
FTIR, and atomic force microscopy and compare them to brushes synthesized
by the traditional growing-from approach. Finally, we demonstrate
that several properties of the zwitterionic polymer brush prepared
by our passing-through method, for example, wettability, grafting
density, uniformity, salt permeation retardation, and fouling resistance,
are superior to those of brushes prepared by the growing-from technique.
The
interfacial spreading and exfoliation of graphene was used
to create low-density, hollow microspheres defined by a thin shell
of graphene. The spheres were templated by a thermodynamically driven
self-assembly process in which graphite spontaneously exfoliated and
spread at the high-energy interfaces of a water-in-oil emulsion. Graphene
thus acted as a 2D surfactant to stabilize the dispersed water droplets
utilized as polymerization templates. Using a mixture of organic solvent
and monomer as the emulsion oil phase, polystyrene-coated hollow graphene
microspheres were created. These spheres were characterized by optical
and electron microscopy, thermo-gravimetric analysis, nanoindentation,
and particle sizing. The mechanism leading to the microsphere surface
morphology and shape is discussed, with the oil phase composition
shown to play a critical role.
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