(364d) Glad Sculptured Thin Films Functionalized with Polymer Brushes

GLAD
Sculptured Thin Films Functionalized with Polymer Brushes

Tadas Kasputis^1,5, Meike
Koenig², Daniel Schmidt^3,5, Klaus-Jochen Eichhorn²,
Petra Uhlmann², Mathias Schubert^3,4,5, Manfred Stamm²,
Angela K. Pannier^1,4,5

¹Department of Biological
Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

²Leibniz Institute of
Polymer Research Dresden, Hohe Straµe 6, 01069 Dresden, Germany

³Department of Electrical
Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

⁴Nebraska Center for
Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588,
USA

⁵Center for Nanohybrid
Functional Materials, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

Abstract

The development
of stimuli-responsive surface coatings has been the subject of many
investigations in the recent past. Polymer brushes, consisting of polymeric
macromolecules tethered on one end to an underlying substrate, are regarded as
very promising candidates because these systems are capable of responding to
external stimuli such as temperature or pH, generally by reversible
swelling-deswelling behavior. Another major focus of modern material science
and engineering is the fabrication of three-dimensional nanostructures
possessing tunable intricate features such as porosity, surface roughness, and
surface chemistry. In this study, nanostructures with slanted columnar surface
morphologies were functionalized with polymer brushes to fabricate a dual
featured surface in which the intercolumnar spaces of the nanostructures are
filled with polymer brushes. Specifically, the nanostructures were fabricated
by glancing angle deposition (GLAD) of silicon onto gold. Guiselin polymer
brushes, consisting of polyacrylic acid were reacted to the slanted columns by
a grafting-to approach using a poly(glycidymethacrylate) anchoring layer. Generalized
ellipsometry (GE) was employed to characterize the fabrication of the GLAD
sculptured thin film (STF) as well as the step-wise reaction of polymer brushes
to the GLAD nanostructures. Furthermore, in-situ combinatorial spectroscopic
ellipsometry and quartz crystal microbalance with dissipation studies were
conducted to evaluate the reversible swelling characteristics of functional
polymer brushes. This study demonstrates that GLAD STFs are capable of
withstanding the grafting-to process. GE was also shown to be an accurate probe
of monitoring hybridization of materials within complex nanostructures.
Together with post-fabrication analysis, GE demonstrates
that polymer brushes are successfully immobilized within the GLAD STF and that
the brushes exhibit reversible swelling characteristics. These complex and
tunable hybrid nanostructures with stimuli-responsive characteristics provide
novel material surfaces for nanoelectronics, biotechnology, and a variety of
other advanced material applications.