Surface properties spreading

Surface Flame Spread 14.3.4.1 Pertinent Material Properties... 

Limited mobility of the molecules of solids. The essential difference between liquids and solids is that the particles of liquids can move, easily, long distances, while those of solids are practically fixed in position. The effects of this limited mobility, on their surface properties, are of two principal kinds. In the first place, those properties of liquid surfaces which are due to the free motion of the particles are absent, or very much less conspicuous, in solids. Thus solid surfaces do not contract spontaneously as a general rule, and it will be seen in Chapter VI that liquids do not spread over the surface of solids to form surface films, nearly as easily as they do on liquids, even when the attraction of the liquid for the solid is great enough for such a film, once spread, to be very stable. 

This second example demonstrates that the SU-8-based micro/ nanostructured surfaces allow for rapid binding and manipulation of hydropho-bically modified DNA at SU-8 surfaces and its controlled release by lipid film spreading. Using a combination of nano- and micro-meter-sized SU-8 patterns, DNA concentration gradients in solution can be created d3mamically. Moreover, other molecules with different hydrophobicites can likely be used such that the hydrophobicity of the molecules can be exploited as a sorting tool to modify surface properties of SU-8. It is, furthermore, possible to heat... 

To test this model, the surface properties of the 22-kDa fragment at an air—water interface have been examined. The air—water interface system has been used extensively to model the interaction of apoli-poproteins with lipid (Phillips and Sparks, 1980 Shen and Scanu, 1980 Camejo and Munoz, 1981 Phillips and Krebs, 1986). When the 22-kDa fragment was spread as monomolecular film in a Langmuir trough, the surface pressure-molecular area isotherm was calculated to be —16 A /... 

Monomolecular layers and LB-multilavers. Compound 21 exhibits amphiphilic properties. Spreading at the air-water interface leads to the formation of oriented monomolecular layers. The monolayer forms a solid condensed phase at 20 C with a collapse pressure near SOmN/m. It can easily be transferred onto various hydrophobic substrates such as CaF, ZnS, AgCl, Si, Ga or metal surfaces, and Langmuir-Blodgett-type multilayers (21> of variable thickness can be built up. These multilayers also exhibit a rapid reaction if exposed to UV- or y-irradiation. From an infrared spectroscopic study described recently (ll-JA) a 1,4-addition reaction is evident, as it also occurs in microcrystalline powders of 21- The solid state polymerization of 21 is schematically represented by Figure 14. 

---