Authors Mikhailova, Y. ; Pigorsch, E. ; Grundke, K. ; Eichhorn, K.-J. ; Voit, B.
Title Surface properties and swelling behaviour of hyperbranched polyester films in aqueous media
Date 14.05.2004
Number 11931
Abstract Thin films of hydroxyl (POH) and carboxyl (PCOOH) terminated aromatic hyperbranched polyesters (HBPs) were prepared by spin coating on silicon wafers and subsequently annealed above their glass transition temperature (T<SUB>g</SUB>). The surface properties and the swelling behaviour of these films in aqueous buffer solutions were studied as a function of annealing time using contact angle measurements and ellipsometry. Non-annealed films were hydrophilic with surface free energies of 51 mJ/m<SUP>2</SUP> for POH and 49 mJ/m<SUP>2</SUP> for PCOOH, respectively. The swelling behaviour of the polymer films in buffer solution with pH 7.4 was described in terms of changes of the thickness and effective refractive index of the swollen layer. Under identical conditions a lower water uptake was found for hydroxyl terminated HBPs (POH) which were annealed more then 2 h. The lower water uptake correlates with the surface properties of the films. The annealed films were less hydrophilic. Their surface free energy was 38 mJ/m<SUP>2</SUP> independent of the annealing. Films of carboxyl terminated HBPs (PCOOH) showed similar surface properties after annealing. However, these films were unstable under the same conditions in aqueous solutions. Stable PCOOH films were obtained by additional covalent binding to the substrate using an epoxy silane as a coupling agent.
Publisher Macromolecular Symposia
Wikidata Q57778084
Citation Macromolecular Symposia 210 (2004) 271-280
Tags grafting to hyperbranched polymers surface free energy swelling behaviour contact-angle interpretation drop shape-analysis polymer-films thin-films layers

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