Application of the JKR method to the measurement of adhesion to Langmuir-Blodgett cellulose surfaces

The JKR method has been applied for studying adhesion between poly(dimethyl siloxane) (PDMS) caps and Langmuir-Blodgett cellulose surfaces including th e substrate, hydrophobized mica, and two flat mineral surfaces, bare mica a nd glass, The self-adhesion of PDMS caps and oxidized PDMS caps are include d as a reference to compare with literature data. The results of the measur ements have been compared with previous studies using the surface force app aratus and similar systems. A satisfactory agreement is obtained for simple systems showing no, or very limited, hysteresis between loading and unload ing curves, In several cases, however, a large hysteresis is found between loading and unloading curves, with a larger adhesion measured from the pull -off force than from the JKR-curve determined on loading. This is, for inst ance, the case for PDMS against cellulose. The situation is analogous to th at found in wetting studies showing a large hysteresis between advancing an d receding contact angles. (C) 2000 Academic Press.