Wafer-scale synthesis of defined polymer brushes under ambient conditions

Abstract

A method is presented that allows for the first time the preparation of highly defined polymer brush coatings on the wafer-scale under ambient conditions (room temperature, exposure to air) from a broad variety of monomers. The discovered high oxygen-tolerance of the surface-initiated Cu(0)-mediated controlled radical polymerization (SI-CuCRP) yields entire wafers homogeneously covered by a polymer brush of linear, high molar mass polymers with narrow dispersities (Đ = 1.1) at extremely high grafting densities (≈1 chain per nm 2 ). The low-tech and air tolerant method requires only ≲4 mL reaction solution containing a monomer and a ligand between two facing substrates. Thus, the SI-CuCRP is scalable to any surface area with minimal costs and minimal equipment. Despite the simplicity of the method, the high endgroup fidelity of SI-CuCRP is demonstrated by the preparation of a tetrablock copolymer brush which is the first example of a higher order block copolymer brush prepared by any surface-initiated polymerization. Finally, we present a new facile lithographic technique, the copper plate proximity printing (CP 3 ), which relies on the proximity of the bulk copper surface to the initiator-bearing substrate. The CP 3 is resist-and development-free and transfers the copper plate profile (of a copper coin) directly into an image composed of a 3D polymer brush. † Electronic supplementary information (ESI) available. See

“On Water” Surface‐initiated Polymerization of Hydrophobic Monomers

“…[4] Recently,w eo ptimized the CuCRP for polymer brush synthesis via surface-initiated polymerization CuCRP (SI-CuCRP) by simply using ac opper plate as the catalyst, al igand and the monomer of choice but no additional Cu I/II sources. [5] TheSI-CuCRP was found to be the fastest SI-CRP for many monomers,a nd resulted in very dense brushes and homogeneous brushes even on the wafer scale. [5a-c, 6] Very recently,t his method was also successfully adopted for SI-ATRP.…”

“…Thegap was filled with either of both phases (Figure 1b and c) and the assembly was left under ambient conditions for polymer brush growth by SI-CuCRP as reported before. [5,11] Surprisingly,n op olymer brush formation was observed using the organic phase.H owever,w ith the lower aqueous phase (mainly water with at iny amount of monomer aggregates and dissolved monomer unimers) ahomogeneous 68 nm thick PMMA brush was obtained in only 1hreaction time ( Figure 1d). In further experiments,w ef ound that the polymer brush growth rate (d)c an be increased by adding as mall amount of methanol as ap rotic co-solvent following the arguments on the reaction acceleration for "on water" reactions ( Figure 1d).…”

“On Water” Surface‐initiated Polymerization of Hydrophobic Monomers

“…The assembly was done on a benchtop under normal atmosphere (Figure c). Analog to our previous report, this most simple methodology allows the preparation of polymer brushes of choice from hydrophobic vinyl monomers under ambient conditions and is basically scalable to any substrate size …”

“…Very recently, this method was also successfully adopted for SI‐ATRP . Analog to CuCRP in solution or SI‐ATRP, the SI‐CuCRP is significantly accelerated in water or aqueous solutions, hydrophilic monomers showed the highest brush layer growth rate ( δ ) and were remarkably oxygen tolerant . However, for the conversion of hydrophobic monomers such as many acrylates and methacrylates the SI‐CuCRP was performed intuitively in organic solvents and required an inert atmosphere.…”

Hierarchical comb brush architectures via sequential light-mediated controlled radical polymerizations

“…Although useful, arbitrary spatial control of complex polymer brush architectures could not be achieved by this method. For arbitrary patterning, lithographic techniques such as photolithography, electron beam lithography, and soft lithography have been extensively used and offer excellent capabilities; however, these methods are often time‐consuming, expensive, and destructive in nature …”