• Mihhels, Karl
• Johnson, C. Magnus
• Lepikko, Sakari
• Kotov, Nikolay
• Xu, Wenyang
• Kontturi, Eero
• Ras, Robin
• Pettersson, Torbjörn

Abstract

<p><i>Hypothesis</i>: 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. </p><p><i>Experiments</i>: 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. </p><p><i>Findings</i>: Adsorbed layers from low molecular weight PS were disrupted with typical spinodal decomposition patterns whereas high molecular weight (&gt;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.</p>

Topics

• impedance spectroscopy
• surface
• polymer
• experiment
• melt
• spinodal decomposition
• Silicon
• molecular weight