title: Reduced Lateral Confinement and Its Effect on Stability in Patterned Strong Polyelectrolyte Brushes.
abstract: The stability of strong polyelectrolyte brushes (PEBs) was studied in bulk and in patterned structures. Thick PEBs of poly([(2-methacryloyloxy)ethyl]trimethylammonium chloride) with thicknesses >100 nm were synthesized using single electron transfer living radical polymerization. Brush patterning was identified using deep-ultraviolet photolithography by means of either a top-down (TD) or bottom-up (BU) method, with features as small as 200 nm. The brushes were soaked in water under a range of pH or temperature conditions, and the hydrolysis was monitored through dry-state ellipsometry and atomic force microscopy measurements. BU patterns showed reduced degrafting for smaller patterns, which was attributed to increased stress relaxation at such dimensions. In contrast to the already relaxed BU-patterned brush, a TD-patterned brush possesses perpendicular structures that result from the use of orthogonal lithography. It was found that the TD process induces cross-linking on the sidewall, which subsequently fortifies the sidewall materials. This modification of the polymer brushes hindered the stress relaxation of the patterns, and the degrafting trends became irrelevant to the pattern sizes. With proper tuning, the cross-linking on the sidewall was minimized and the degrafting trends were again relaxation-dependent.
authors.forename: Wei-Liang
authors.identifier: 0000-0003-2581-1996
authors.initials: WL
authors.lastname: Chen
authors.affiliation: Department of Microsystems Engineering (IMTEK), University of Freiburg , 79110 Freiburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Menzel
authors.affiliation: Department of Applied Chemistry, Tokyo Metropolitan University , Hachioji 192-0397, Tokyo, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Microsystems Engineering (IMTEK), University of Freiburg , 79110 Freiburg, Germany.
authors.forename: Oswald
authors.initials: O
authors.lastname: Prucker
authors.affiliation: Department of Microsystems Engineering (IMTEK), University of Freiburg , 79110 Freiburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Rühe
authors.forename: Christopher K
authors.identifier: 0000-0002-3805-3314
authors.initials: CK
authors.lastname: Ober