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    Solid-state polymer adsorption for surface modification: The role of molecular weight

    Year: 2022

    Journal: J. Colloid Interface Sci., Volume 605, JAN, page 441–450

    Authors: Xu, Wenyang; Mihhels, Karl; Kotov, Nikolay; Lepikko, Sakari; Ras, Robin H. A.; Johnson, C. Magnus; Pettersson, Torbjorn; Kontturi, Eero

    Organizations: Tandem Forest Values; Olle Engkvists Stiftelse (Sweden)

    Keywords: Contact angle; Dewetting; Polymer adsorption; Polystyrene; Silicon wafers; Surface modification

    Hypothesis: Solid-state polymer adsorption offers a distinct approach for surface modification. These ultrathin, so-called Guiselin layers can easily be obtained by placing a polymer melt in contact with an interface, followed by a removal of the non-adsorbed layer with a good solvent. While the mechanism of formation has been well established for Guiselin layers, their stability, crucial from the perspective of materials applications, is not. The stability is a trade-off in the entropic penalty between cooperative detachment of the number of segments directly adsorbed on the substrate and consecutively pinned monomers. Experiments: Experimental model systems of Guiselin layers of polystyrene (PS) on silicon wafers with native oxide layer on top were employed. The stability of the adsorbed layers was studied as a function of PS molecular weight and polydispersibility by various microscopic and spectroscopic tools as well as quasi-static contact angle measurements. Findings: Adsorbed layers from low molecular weight PS were disrupted with typical spinodal decomposition patterns whereas high molecular weight (>500 kDa) PS resulted in stable, continuous layers. Moreover, we show that Guiselin layers offer an enticing way to modify a surface, as demonstrated by adsorbed PS that imparts a hydrophobic character to initially hydrophilic silicon wafers. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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