ma9b00597_si_001.pdf (1.69 MB)
“Structurally Neutral” Densely Packed Homopolymer-Adsorbed Chains for Directed Self-Assembly of Block Copolymer Thin Films
journal contribution
posted on 2019-07-02, 00:00 authored by Yuma Morimitsu, Daniel Salatto, Naisheng Jiang, Mani Sen, Shotaro Nishitsuji, Benjamin M. Yavitt, Maya K. Endoh, Ashwanth Subramanian, Chang-Yong Nam, Ruipeng Li, Masafumi Fukuto, Yugang Zhang, Lutz Wiegart, Andrei Fluerasu, Keiji Tanaka, Tadanori KogaWe here report that
adsorbed chains composed of one of the constituent
blocks can be used as a new surface modification approach to induce
perpendicularly oriented lamellar microdomains in block copolymer
thin films. A nearly symmetric polystyrene-block-poly(methyl
methacrylate) (PS-block-PMMA) diblock copolymer was
used as a model. Densely packed PS- or PMMA-adsorbed chains of about
2–3 nm in thickness (“polymer nanocoatings”)
were deposited on silicon (Si) substrates using a solvent-rinsing
approach. Spin-cast films of 40 or 60 nm-thick PS-block-PMMA (equivalent to two or three interdomain spacings) were subsequently
deposited onto the PS or PMMA nanocoatings. Grazing incidence small-angle
X-ray scattering experiments revealed the formation of perpendicularly
oriented lamellar microdomains within the entire films at 200 °C,
where balanced interfacial interactions at the polymer–air
interface were achieved. Additionally, X-ray photon correlation spectroscopy
studies demonstrated the dynamics of the fully standing lamellar microdomains
in the melt, which are coupled to cooperative interdomain movement.
We demonstrate that the “neutrality” of the nanocoating
is attributed to its noninteractive property against both blocks.
This “structurally neutral” property prevents adsorption
of the PS-block-PMMA chains on the bare Si substrate
that causes the undesirable substrate field effect.