Affective interactions, solid surface polymer

Surface properties In the interaction of polymers with other materials (liquid or solid), surface properties are critical, (a) The interaction of polymer surfaces with liquids in this case, the important phenomena are the wetting and spreading and these affect the adhesion of polymer surfaces applied in the Uqnid state. When a liquid is brought into contact with a polymeric sohd, the extent of wetting is described by the contact angle 0 which a hquid droplet makes with the surface at the three-phase contact hne. When a hquid wets a polymeric sohd to the extent that the contact angle becomes zero, the equilibrium spreading coefficient S is defined as in Eq. 1.16 ... 

There are a number of interaction forces, which can exist between particles—attractive van der Waals, repulsive electrostatic, structural and solvation forces, forces due to adsorbed and non-adsorbing polymer etc. These forces can be manipulated by a variety of different means—by adding salt to screen the charge on the particles, to index match the solvent and particles to screen van der Waals interactions and changing the solvency to affect the state of the adsorbed polymer to name a few. The chemical sensitivity of these interactions becomes particularly important when dealing with sub-100 nm particles or for situations where particles are held at separations on the order of a few nanometers. In both cases, the granularity of the continuous phase and chemical details of the interactions of the species in solution with the solid surface begin to dominate interactions. If conditions where the particles are held at small separations are of interest, these interactions must be characterized, as they cannot at present, be predicted. 

Up to now we have outlined the polymer properties. What about the surface itself Clearly, any adsorption process will be sensitive to the type of surface and its internal structme. As a starting point we assume that the solid surface is atomically smooth, flat, and homogeneous, as shown in Fig. 4a. This ideal solid surface is impenetrable to the chains and imposes on them a surface interaction. The surface potential can be short ranged, affecting only the monomers which are in direct contact with the substrate or in close vieinity of the surface. In other eases, the surface can have a longer range effect, like van der Waals, or eleetrostatie interactions, if it is charged. 

The adsorption of a surfactant molecule onto a solid surface can be significantly affected by relatively small changes in the characteristics of the system. Such sensitivity results from the wide range and strengths of adsorption mechanisms that may be operative. Except in some cases of surfactant-polymer interaction discussed in Chapter 7, it is usually found that adsorption occurs on a molecular... 

There are some uncontrollable factors affecting the determination of critical surface tension—e.g., the type of liquids used, the type of interaction between a liquid and a solid, the homogeneity of surface, etc. An ideal correlation should be made from the direct surface tension, if available, of a polymer melt. 

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