Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 4: Thin Polymer Films
CPP 4.1: Vortrag
Dienstag, 3. April 2001, 15:45–16:05, 111
Hydrophobicity of Homo-and Copolymer Surfaces — •valerie andre1, Martin reif2, and ingolf kuehn3 — 1BASF Aktiengesellschaft,Polymer Physics/ Solid State Physics, 67056 Ludwigshafen — 2Polymer Dispersions — 3Business Unit Paper Chemicals
In order to determine the hydrophobicity of different homo-and copolymers, the advancing and receding contact angles of water have been measured on specially prepared films. The polymerisation of the monomers (styrene, methylacrylate, butylacrylate, ethylhexylacrylate) was carried out with little surfactant and a hydrophobic iniator (t-Butyperoctoat). The polymers were washed and very smooth films were obtained with spin-coating. The difference between advancing and receding contact angles (hysteresis) increases with the mobility of the polymer chains (decreasing glass transition temperature)caused by the reorientation of the groups during the wetting. Therefore polymers with a low Tg like polyethylhexylacrylate, which would be expected hydrophobic show a hydrophilic behavior after wetting (contact angle 20 degrees). They also display a high hysteresis (above 40 degrees), probably due to an increased roughness. The absence of surface active molecules and salts was checked with TOF-SIMS. The influence of the polymer architecture (cross-linking, molecular weight) on its hydrophobicity will also be discussed in the paper.