Authors Grundke, K. ; Michel, S. ; Eichhorn, K.-J. ; Beyerlein, D. ; Bayer, Th.
Title Influence of Chemical Interactions on the Macroscopic Spreading of a Maleic Anhydride Copolymer Melt
Date 07.06.2002
Number 10102
Abstract We report on wetting experiments of a maleic anhydride copolymer melt on smooth horizontal silicon wafers which were either cleaned or coated with a crosslinked network of a poly(aminosiloxane). The surface properties of the solid substrates have been controlled using contact angle and zeta potential measurements, FT-IR attenuated total reflection (ATR) spectroscopy, and atomic force microscopy. Compared to the bare silicon wafer surface, which had a surface free energy of 61 mJ·m<SUP>-2</SUP> and a weakly acidic surface character due to silanol groups, the poly(aminosiloxane) layer is characterized by basic amino groups at the outermost surface (pH<SUB>IEP</SUB> &gt; 9) and a lower surface free energy (<I><IMGSRC="/giflibrary/12/gamma.gif"BORDER="0"></I><SUB>sv</SUB> = 47 mJ·m<SUP>-2</SUP>). The results of the wetting experiments indicate clearly that macroscopic spreading of the maleic anhydride copolymer melt can be influenced by strong interactions at the solid-liquid interface near the triple line. As could be shown by FT-IR microscopy and spectroscopic ellipsometry, an interfacial chemical reaction takes place between the amino groups available on the solid poly-(aminosiloxane) surface and the anhydride groups of the copolymer melt to form imide structures at the solid-liquid interface during wetting. Due to this interfacial chemical reaction, the spreading process of the maleic anhydride copolymer melt was slowed down and the contact angle was time-dependent indicating a non-equilibrium system. It is also remarkable that lower contact angles were obtained after a certain time of contact compared to the non-reactive system, though the surface free energy of the solid substrate was lower in the reactive system. We assume that the increase of the spreading force at a given spreading speed is due to the release of the free energy during the interfacial reaction, indicating that the chemical reaction is an additional driving force within the spreading process.
Publisher Macromolecular Chemistry and Physics
Citation Macromolecular Chemistry and Physics 203 (2002) 937-946
Tags PG_SurfaceTension , PG_Wetting_ContactAngle

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