Roughness-Mediated SI-Fe0CRP for Polymer Brush Engineering toward Superior Drag Reduction.

Surface-initiated iron(0)-mediated controlled radical polymerization (SI-Fe0CRP) with low toxicity and excellent biocompatibility is promising for the fabrication of biofunctional polymer coatings. However, the development of Fe(0)-based catalysts remains limited by the lower dissociation activity of the Fe(0) surface in comparison to Cu(0). Here, we found that, by simply polishing the Fe(0) plate surface with sandpaper, the poly(methacryloyloxy)ethyl trimethylammonium chloride brush growth rate has been increased significantly to 3.3 from 0.14 nm min-1 of the pristine Fe(0) plate. The excellent controllability of roughness-mediated SI-Fe0CRP can be demonstrated by customizing multicompartment brushes and triblock brushes. Furthermore, we found that the resulting polymer brush coatings exhibit remarkably low water adhesion (0.097 mN) and an outstanding drag reduction rate of 52% in water. This work provides a promising strategy for regulating the grafting rate of polymer brushes via SI-Fe0CRP for biocompatible marine drag reduction coatings.

Seawater-Boosting Surface-Initiated Atom Transfer Radical Polymerization for Functional Polymer Brush Engineering.

Iron-mediated surface-initiated reversible deactivation radical polymerization (Fe0 SI-RDRP) is an appealing approach to produce robust polymer surfaces with low toxicity and biocompatibility, while its application has been limited so far due to the poor activity of iron-based catalysts. Herein, we show that the iron(0)-mediated surface-initiated atom transfer radical polymerization (Fe0 SI-ATRP) could be significantly enhanced by simply using seawater as reaction media. In comparison, there was no polymer brush formation in deionized water. This method could convert a range of monomers to well-defined polymer brushes with unparalleled speed (up to 31.5 nm min-1) and a minor amount of monomer consumption (µL). Moreover, the resultant polymer brush shows chain-end fidelity which could be exemplified by repetitive Fe0 SI-ATRP to obtain tetrablock brushes. Finally, we show the preparation of polymer-brush-gated ion-selective membranes by Fe0 SI-ATRP for osmotic energy conversion, which gives excellent power densities of 5.93 W m-2, outperforming the most reported as well as commercialized benchmark (5 W m-2).