Weak Polyelectrolyte Brush Arrays Fabricated by Combining Electron-Beam Lithography with Surface-Initiated Photopolymerization

Abstract

We present a simple “top-down/bottom-up” strategy to fabricate nano- and micropatterned polymer brush arrays composed of pH- and salt-sensitive, weak polyelectrolyte copolymers [poly(N-isopropylacrylamide-co-methacrylic acid, 3:1, poly(NIPAAM-co-MAA)]. In our approach, a silicon surface is first patterned with gold, using “lift-off” electron-beam lithography (“top-down”), and the resulting pattern is then amplified by surface-initiated photopolymerization by conventional, UV-light-induced free radical polymerization (“bottom-up”) from an immobilized 2,2‘-azobisisobutyronitrile (AIBN) type initiator. The use of pH- and ionic-strength-sensitive comonomers in the copolymer brush enables large, externally triggered conformational changes of the micro- and nanopatterned polymer brushes. We observed that the height of nanopatterned ionized polymer brushes increases with increasing feature size of the pattern. The design and fabrication of surfaces with conformationally switchable, patterned polymeric structures is important for sensing and actuation applications on the micro- and nanoscales.

Micro- and Nanostructured Poly[oligo(ethylene glycol)methacrylate] Brushes Grown From Photopatterned Halogen Initiators by Atom Transfer Radical Polymerization

“…Kaholek et al also noted that their nanopatterned brushes exhibited smaller heights than bulk films patterned under identical conditions. 39 They attributed this to the lower density of brushes in the nanostructures. Our data suggest similar behavior: close packing of polymer chains is required to achieve a dense upright brush, but for small structures, as the line width starts to approach the radius of gyration of the polymer, this is much harder to achieve.…”

“…36,37 At smaller length scales, dip-pen nanolithography has been used in an analogous fashion to deposit initiators in patterns from which poly͑N-isopropylacrylamide͒ ͑NIPAAM͒ brushes have been grown. 38,39 Schuh et al fabricated gradients, consisting of a continuously varying density of brushes, by using an interferometer to degrade a photoinitiator-functionalized surface. 36 In the present work, we explore a rapid simple approach to brush patterning based on the dehalogenation of a bromoor chlorofunctionalized surface.…”

Characterization of patterned poly(methyl methacrylate) brushes under various structures upon solvent immersion

“…The generation of complex patterns in polymer films is traditionally achieved by using a combination of spin-casting and photolithographic techniques [20]. Current commercial lithographic processes can generate patterns with perfection over macroscopic areas and with dimensional control of features, registration, and overlay within tight tolerances and margins.…”

Stimuli response of cationic polymer brush prepared by ATRP: Application in peptide fractionation

“…These polymer brushes are termed “responsive polymer brushes” or “smart materials” and they are of value in polymer science because of their wide range of technological applications. For instance, polymer brushes have been used in various applications such as protein fractionation, 2 anti-fouling, 3 environmentally responsive polymers, 2b,3b,4 bio- and chemical sensing, 5,6,7 cell adhesion and wetting, 3,4,8,9 microfluidics, 10 microfabrication, 3a,6b molecular recognition, 11 and optics. 12 …”