DYNAMICS OF THE SPREADING OF CHAIN-LIKE MOLECULES WITH ASYMMETRIC SURFACE INTERACTIONS

In this work we study the spreading dynamics of tiny liquid droplets o n solid surfaces in the case where the ends of the molecules feel diff erent interactions with respect to the surface. We consider a simple m odel of dimers and shea chainlike molecules that cannot form chemical bonds with the surface. We use constant temperature molecular dynamics techniques to examine in detail the microscopic structure of the time -dependent precursor film. We find that in some cases it can exhibit a high degree of local order that can persist even for flexible chains. Our model also reproduces the experimentally observed early- and late -time spreading regimes where the radius of the film grows proportiona l to t(0.5). The ratios of the associated transport coefficients are i n good overall agreement with experiments. Our density profiles are al so in good qualitative agreement with measurements on the spreading of molecules on hydrophobic surfaces.