SYNTHESIS AND SURFACE-ENERGY MEASUREMENT OF SEMI-FLUORINATED, LOW-ENERGY SURFACES

The surface energy and stability of pendent semifluorinated groups (SF G) attached to the surface of PDMS were measured using the JKR techniq ue. SFG, made up of a flexible hydrocarbon segment and a mesogen, i.e. , the fluorocarbon segment, combine the low surface energy aspect of a (-CF2-) and (-CF3) surface with a resistance to surface reconstructio n. An acid chloride group present on the end of the hydrocarbon segmen t allowed the SFG eo be covalently attached to the surface of hydrolyz ed elastomeric PDMS model networks. Whereas the hydrolyzed PDMS surfac es had surface energies of 1-10 J/m(2) and showed large adhesion hyste resis, the SFG-treated surfaces displayed a minimum adhesion hysteresi s and had a surface energy of similar to 14.5 mJ/m(2). This result sug gests that in the SFG-modified surfaces both (-CF2-) and (-CF3) groups cover the surface. As the extent of hydrolysis of the PDMS networks i ncreased, the density of attached SFG increased (as shown by XPS resul ts), but the surface energy remained constant. No effect of length of time the networks were kept in contact or the rate of unloading was ob served.