MODIFICATION OF THE SURFACE FREE-ENERGY COMPONENTS OF A POLYMER BY ADSORPTION OF POLY(OXYETHYLENE)-POLY(OXYPROPYLENE) BLOCK COPOLYMERS

To study the wettability-increasing effect of poloxamer adsorption on calcium alginate microfibres, poloxamer films were deposited from aqueous solution on glass substrates and on glass coated with calcium alginate. By measuring the contact angles with water, glycerol, and diiodomethane, an estimate could be made of the dispersion (Lifshitz-van der Waals) and acid-base surface free energy components of these composite surfaces. By depositing different A-B-A block co-polymer surfactants (where A is more hydophilic than B), it is possible to increase the wettability of polar or non-polar solid surfaces by non-polar or polar liquids, respectively. This increase in wettability is obtained by the adsorption of the co-polymer surfactant via the hydrophilic blocks on polar substrates or by the adsorption of the co-polymer surfactant via the hydrophobic blocks on apolar substrates. However, possible reorientations of the A or B blocks towards the test liquid, which are enhanced at a high adsorption level, by the flexibility of the blocks can induce an increase in the wettability of both (polar or non-polar) substrates by both (polar or non-polar) liquids.