Iron-mediated surface-initiated reversible deactivation radical polymerization (Fe 0 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 (Fe 0 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 Fe 0 SI-ATRP to obtain tetrablock brushes. Finally, we show the preparation of polymer-brush-gated ion-selective membranes by Fe 0 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 ).

Here we present a facile and robust strategy, namely, galvanic-replacement-assisted surface-initiated Cu(0)mediated atom transfer radical polymerization (gr-SI-Cu 0 ATRP, or gr-SI-Cu 0 CRP) for polymer brush engineering under ambient conditions. In gr-SI-Cu 0 ATRP, highly active and nanostructured Cu(0) surfaces are obtained by a simple galvanic replacement on zinc/aluminum surfaces in dilute Cu 2+ solution. Polymer brush growth rate is extremely high (up to ∼904 nm in 30 min polymerization); meanwhile, both nano Cu(0) surfaces and Cu 2+ solution can be reused multiple times without losing grafting efficiency. We also demonstrate that the gr-SI-Cu 0 ATRP is advantageous for polymer brush engineering on arbitrary substrates, including flexible (polyethylene terephthalate), curved (polycarbonate), and porous (anodic aluminum oxide), and endow the substrates with various functionalities, for example, anti-icing, antifogging, and ion selectivity.