I didn't find a cut-and-pasteable source, but what I found was that wax is not a pure compound; it is many compounds working together, linked by covalent bonding, performing many complex functions in its original occurence; mostly protection and permeability at the same time. The covalent bonds act between molecules to form the net or film, and also bond to the surface that the wax is applied to, usually covalently, but at least in the case of MPPP, cationically (I know this because
Meg's states so specifically). The outer surface of the film presents no sites for other molecules to bond to (sometimes, depending on scale, experienced by us physically as "slickness"). I don't know if aminofunctional silicones bond covalently or cationically, I didn't look it up.
Tom