Modification of the Surface Properties of Polymers

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The interfacial free energy between a polymer and water is relatively large. As a result, proteins, platelets and cells will deposit upon its surface. By modifying the surface properties of the polymers, one can reduce the interfacial free between them and water, and thus reduce the thermodynamic driving force for deposition. The following surface modification technique, which employs two immiscible liquids in contact, will be investigated. One of the liquids is water and contains a water soluble surfactant, while the other liquid is an organic compound which is selected so as to be a solvent for the polymer substrate. It is convenient for the organic phase to be more dense than water. The substrate is introduced for a short time in the organic phase. This softens its surface and allows the entanglement of the hydrocarbon chains of the surfactant molecules and of the surface molecules of the polymer substrate during the pulling out of the substrate through the water-organic solvent interface and the water phase. The two-phase system provides an interface at which the surfactant molecules adsorb. This highly oriented surfactant layer increases the efficiency of the transfer of surfactant to the substrate. The interfacial free energy between the modified polymer surface and water is thus decreased below 1 dyne/cm. This can reduce the deposition of proteins, cells and platelets on such surfaces. The adsorption of proteins on the non-modified and surface as well as the stability of the modified surface will be investigated to verify the effectiveness of the procedure.