No abstract

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.