Kalorimetrische Untersuchungen zur Adsorption von Makromolekülen aus verdünnten Lösungen

By means of a highly sensitive calorimeter the enthalpies of adsorption of polyethyleneglycols from benzene-, water-and methanol-solutions on fine-grained silica (SiO₂) are measured within the total range of coverages. For collating the values obtained at varying weighed samples of polymer the adsorption isotherms are ascertained supplementarily. The monotonous falling of the differential adsorption enthalpies with increasing adsorbed amount yields a decrease of the number of adhered segments with coverage. From the comparison of the enthalpy-values in the range of the rise and the saturation of the isotherms with the enthalpy-contribution of the hydrogen bond as well as from the comparison of the adsorbed number of monomers with the OH-group-density on the adsorbent surface results, that the macromolecules adsorbs at low coverages in a flat lying form and coils up with increasing coverage, corresponding to a falling number of adhered segment. Due to the interaction between solvent and adsorbent, which is competitive to that one between polymer and adsorbent, the amount of the heat of wetting is decisive for the value of the adsorption enthalpy.