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

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.

Grafting of Poly(ionic liquid) Brushes through Fe0-Mediated Surface-Initiated Atom Transfer Radical Polymerization for Marine Antifouling

Surface-tethered poly(ionic liquid) brushes have attracted considerable attention in widespread fields, from bioengineering to marine antifouling. However, their applications have been constrained due to the poor polymerization efficiency and sophisticated operation process. In this work, we efficiently synthesized the poly(ionic liquid) brushes with unparalleled speed (up to 98 nm h-1) through Fe0-mediated surface-initiated atom transfer radical polymerization (Fe0 SI-ATRP) while consuming only microliter of monomer solution under ambient conditions. We also demonstrated that poly(ionic liquid) brushes with gradient thickness and wettability were easily accessible by regulating the distance between the opposite plates of Fe0 SI-ATRP. Moreover, the resultant poly(ionic liquid) brushes presented excellent antibacterial activities against Escherichia coli (99.2%) and Bacillus subtilis (88.1%) after 24 h and low attachment for proteins and marine algae (≤5%) for over 2 weeks. This research provided pathways to the facile and controllable fabrication of poly(ionic liquid) materials for marine antifouling applications.

Magnetically Recyclable Nanoscale Zero-Valent Iron-Mediated PhotoRDRP in Ionic Liquid toward Smart, Functional Polymers

A facile method based on recyclable nanoscale zero-valent iron (nZVI)-mediated photoinduced reversible deactivation radical polymerization in ionic liquid (IL) leads to the synthesis of narrow disperse poly(tert-butyl methacrylate) (PTBMA), amphiphilic PTBMA-block-poly(poly(ethylene glycol)methacrylate) diblock copolymer and double hydrophilic poly(methacrylic acid)-block-poly(poly(ethylene glycol)methacrylate) (PMAA-b-PPEGMA) diblock copolymers thereof. Stimuli response of the synthesized PMAA-b-PPEGMA diblock copolymer against variation in pH and temperature is assessed. Recyclability of the nZVI (catalyst) and IL (solvent) is established. Polymerization may be switched ON or OFF, simply by turning the UVA light irradiation ON or OFF, offering temporal control. The diblock copolymer self-aggregates into spherical nanoaggregates which are employed for encapsulation of coumarin 102 (C102, a typical hydrophobic dye), describing their potential application in drug delivery applications. The facile synthesis strategy may open up new avenues for the preparation of intelligent functional polymers for engineering and biomedical applications.

Surface-Initiated Zerovalent Metal-Mediated Controlled Radical Polymerization (SI-Mt0CRP) for Brush Engineering

ConspectusThe surface-tethered polymer brush has become a powerful approach to tailoring the chemical and physical properties of surfaces and interfaces and revealed broad application prospects in widespread fields such as self-cleaning, surface lubrication, and antibiofouling. Access to these diverse functional polymer brushes is highly dependent on versatile and powerful surface-initiated controlled radical polymerization (SI-CRP) strategies. However, conventional SI-CRP typically requires oxygen exclusion, large amounts of catalysts and monomer solution, and a long reaction time, making it time-consuming and sophisticated. When using a two-plate system consisting of an initiator-bearing substrate and a metal plate, we and our collaborators introduced surface-initiated zerovalent metal-mediated controlled radical polymerization (SI-Mt0CRP). In the SI-Mt0CRP setup, a metal(0) plate (Cu, Fe, Zn, or Sn) is placed proximately to an initiator-functionalized substrate and forms a confined polymerization system which considerably simplifies the synthesis of a wide range of polymer brushes with high grafting densities over large areas (up to the meter scale).In comparison to classical SI-ATRP (catalyzed by metal salts), SI-Mt0CRP demonstrates oxygen tolerance, high controllability, good retention of chain-end functionality, and facile recyclability of the metal catalysts (i.e., metal foil/plate). Taking advantage of the confined geometry of the SI-Mt0CRP setup, polymer brushes with various conformations and architectures are easily accessible while consuming only microliter volumes of monomer solution and without complicated operations under ambient conditions. Owing to these attractive characteristics, SI-Mt0CRP has become a versatile technique for functionalizing materials for targeted applications, ranging from the areas of surface science to materials science and nanotechnology.In this Account, we summarize the recent advances of SI-Mt0CRP catalyzed by zerovalent metals (e.g., Cu, Fe, Zn, and Sn) and highlight the intrinsic advantages of the featured experimental setup, compared with the "classical" SI-CRP in which metal salt, powder, or wire is applied. We further discuss the synthetic features and proposed mechanism of SI-Mt0CRP while emphasizing the various external technologies' (including "on water" reaction, galvanic replacement, lithography, and capillary microfluidic) integrated polymerization systems. We also describe structural polymer brushes, including block copolymers, patterned and gradient structures, and arrayed and binary polymer brushes. Finally, we introduce the diverse polymer brushes that have been prepared using these techniques, with a focus on targeted and emerging applications. We anticipate that the discussion presented in this Account will promote a better understanding of the SI-Mt0CRP technique and advance the future development of practical surface brushing.

Ice-Inspired Polymeric Slippery Surface with Excellent Smoothness, Stability, and Antifouling Properties

Ice is omnipresent in our daily life and possesses intrinsic slipperiness as a result of the formation of a quasi-liquid layer. Thus, the functional surfaces inspired by ice show great prospects in widespread fields from surface lubrication to antifouling coatings. Herein, we report an ice-inspired polymeric slippery surface (II-PSS) constructed by a self-lubricating liquid layer and a densely surface-grafted polymer brush. The polymer brush layer could act as a homogeneous matrix to capture lubricant molecules via strong and dynamic dipole-dipole interactions to form a stable quasi-liquid layer that resembles the ice surface. The II-PSS can be easily fabricated on various solid substrates (e.g., silicon, glass, aluminum oxide, plastics, etc.) with excellent smoothness (roughness of ∼0.4 nm), optical transmittance (∼94.5%), as well as repellence toward diverse liquids with different surface tensions (22.3-72.8 mN m-1), pH values (1-14), salinity, and organic pollutants. Further investigation shows that the II-PSS exhibits extremely low attachment for proteins and marine organisms (e.g., algae and mussels) for over one month. These results demonstrate a robust and promising strategy for high-performance antifouling coatings.

Photoinduced Iron-Catalyzed ATRP of Renewable Monomers in Low-Toxicity Solvents: A Greener Approach

Producing polymers from renewable resources via more sustainable approaches has become increasingly important. Herein we present the polymerization of monomers obtained from biobased renewable resources, employing an environmentally friendly photoinduced iron-catalyzed atom transfer radical polymerization (ATRP) in low-toxicity solvents. We demonstrate that renewable monomers can be successfully polymerized into sustainable polymers with controlled molecular weights and narrow molar mass distributions (Đ as low as 1.17). This is in contrast to reversible addition–fragmentation chain-transfer (RAFT) polymerization, arguably the most commonly employed method to polymerize biobased monomers, which led to poorer molecular weight control and higher dispersities for these specific monomers (Đs ∼ 1.4). The versatility of our approach was further highlighted by the temporal control demonstrated through intermittent “on/off” cycles, controlled polymerizations of a variety of monomers and chain lengths, oxygen-tolerance, and high end-group fidelity exemplified by the synthesis of block copolymers. This work highlights photoinduced iron-catalyzed ATRP as a powerful tool for the synthesis of renewable polymers.