Direct Patterning of Intrinsically Electron Beam Sensitive Polymer Brushes

Abstract

The fabrication of patterned polymer brushes has attracted considerable attention as these structures can be exploited in devices on the nano- and microscale. Patterning of polymer brushes is typically a complex, multistep process. We report the direct patterning of poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly(isobutyl methacrylate) (PIBMA), poly(neopentyl methacrylate) (PNPMA), and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) brushes in a single step by electron beam (e-beam) lithography, to obtain nanopatterned polymer brush surfaces. PMMA, PHEMA, PIBMA, PNPMA, and PTFEMA brushes were grown on silicon substrates via surface-initiated atom transfer radical polymerization. Surface analysis techniques including ellipsometry, contact angle goniometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the thickness, hydrophilicity, roughness, and chemical composition of the polymer brushes. Tapping-mode AFM imaging confirmed the successful electron beam patterning of these brushes. Using this direct patterning method, highly resolved nanostructured polymer brush patterns down to 50 nm lines were obtained. This direct patterning of brushes eliminates the need for complex lithographic schemes. The sensitivity of these polymer brushes toward direct patterning with e-beam was studied and compared. The sensitivity curves indicate that the structure of the e-beam degradable methacrylate polymer has a significant effect on the sensitivity of the polymer brush toward e-beam patterning. In particular, the effect of the chemical functionality at the beta-position to the carbonyl group on the polymer brush sensitivity toward direct patterning was studied using groups of varying size and polarity.

From Self-Assembled Monolayers to Coatings: Advances in the Synthesis and Nanobio Applications of Polymer Brushes

“…The synthesis, processing and characterization of such complex brush structures, for example, mixed brushes [193][194][195][196][197], multiblock copolymer brushes [114,115,198], gradient polymer brushes [199,200], nanopatterned polymer brushes [107,116], polymer carpet/Janus membrane [8,[201][202][203] and polymer nanochannels [114,117] are of great interest from a fundamental as well as technological perspective. Comprehensive understanding of structure-property relationships in well-defined and fully characterized polymer brushes aided by new synthesis as well as predictive modeling can open up newer applications for polymer brushes.…”

“…Top-down patterning through lithography was adapted to pattern polymer brushes synthesized by bottom-up "grafting-from" approach. Rastogi et al reported the direct patterning of several methacrylate-based polymer brushes that were exposed to e-beam lithography resulting in a patterned polymer brush surface [116]. Paik et al further showed that e-beam patterning of P(S-b-MMA) brushes created by SIP led to nanochannels, as the upper layer (PS) was crosslinked (negative tone resist) and the bottom layer (PMMA) was degraded upon e-beam exposure (positive tone resist) [117] (Figure 6b).…”

Free‐Standing Films of Semifluorinated Block Copolymer Brushes from Layer‐by‐Layer Polyelectrolyte Macroinitiators

“…The living nature of the ATRP was evident by the appearance of the fluorine atom which is the elemental marker for the pTFEMA brushes. [52][53][54] The high resolution F 1s signal (690 eV) increased proportionally with increasing LbL brush films as shown in Figure 4 accordance with the LbL technique, as the number of macroinitiator layers deposited on the surface increased so did the initiator density. [38e] Having more layers deposited on the surface translated to increasing active sites available for initiating the polymerization.…”

“…These values of over 1008 are consistent with the hydrophobic nature of the semifluorinated pTFEMA brushes. [43,[52][53][54] Figure 2(c) displays visual representations of the water contact angle taken from the LbL 20 macroinitiator film and its subsequent polymerizations.…”

Characterization of ultra-thin polymeric films by Gas chromatography-Mass spectrometry hyphenated to thermogravimetry

“…For the latter application, polymeric materials, and in particular self-assembling block copolymers, are employed to build up tunable nanomasks for subsequent nano-patterning processes. This approach is widely investigated since it is emerging as a simple, cost-effective, versatile, and scalable technique to generate scaffolds and templates for the fabrication of nano-structured devices [1,2]. In more details, the technology leading to lithographic nanomasks involves a multistep thermal procedure [3][4][5] in which a block copolymers thin film (30 nm) is deposited on an ultra-thin layer (2-9 nm) of a grafted functional random copolymer (RCP), which acts as surface modifier.…”