Surface Films of Polymers and Proteins

High molecular weight polymers, including proteins, also form surface mono-layer films. However, because of the length of the polymer molecules and the complex interactions involved in intra- and interchain interactions, the properties of such films are less distinct and more difficult to determine with 

FIGURE 8.20. Film penetration is a potentially important process in which a monomo-lecular film (a) is modified by the insertion of molecules of a second component from the supporting solution (b). In the process, the second component penetrates the original monolayer film from solution to produce a mixed film with new properties. 

Nonprotein polymer films generally behave similarly to the protein films in terms of their n-A curves, orientation, compressibility, and so on, depending on the nature of the side-chains and the possibilities of nonspecific and specific interactions between neighboring units. 

Silicone polymers and fully fluorinated surface-active materials have been found to be the best candidates for spread monolayer film studies on nonpolar liquids. Because nonpolar liquids are more difficult to manipulate in terms of their solvent properties (e.g., by changing pH, electrolyte content) it is often necessary to talk in terms of adsorbed Gibbs monolayers, rather than true insoluble monolayers. However, sometimes we must take what we can get from nature and make the most of it. 

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