Choice of Coating Level

After deciding on the types of modifier to use, one has to decide on the amount that is needed. Many modifiers are relatively expensive, so it is important not to waste any. Moreover, excess amounts can sometimes lead to deleterious effects. 

The optimum level will depend on the effects that are being sought, as well as factors such as how the modifier reacts with the surface, how well it covers that surface, what the thickness and structure of the coating layer are, and how it interacts with the matrix. Some useful guidelines exist to enable an approximate level to be decided on, but final optimisation usually requires trial and error. 

Reactive sites too closely spaced for complete reaction 

Spacing of reactive sites allows complete reaction and a tightly packed monolayer 

Finally, it must be realised that adsorption onto a surface may not be uniform. There may be patches, several molecules thick, in some places and bare surface in others. 

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