Why is Teflon oliophobic?

[6ies]

Homework Statement

Why is Teflon oliophobic?

Homework Equations

N/A

The Attempt at a Solution

Teflon is a polymere of the tetra fluoro ethylene.

The molecule it's self is completly unpolar, but the bonds are majorly polar with an electronegativity diffrence of 1.5 resulting in a very stong bond requiring 560kJ/mol to disociate.

This is a picture of Teflon by the way, the more greenish centeral atoms are carbon, the outer lighter greenish ones are fluorine.

Seeing as the molecule has no polarity, you would think that it should disolve in oil, however it doesn't, why?

The only reason I can think of is because the molecule is so big that not enough oil can surround it.

 

[Moonbear]

Just so you know, we're not ignoring your question, we just haven't located someone who can help you with this one yet. Do you still need help with it, or have you found an answer elsewhere already?

 

[Astronuc]

Ostensibly, it is the strong C-F bond which provides Teflon with its oliophobic properties.

As for bonding Teflon to metals, as I understand it the metal substrate is normally treated in order to allow it to react with the tetraflurorethylene. Apparently, traditional processes use temperatures up to 1800°F or about 1000°C. However a catalyzed process has been developed which allows Teflon bonding at reduced temperatures -
http://utamagazine.uta.edu/fall_2001/discoveries.html [Broken]

 

[chemisttree]

I consulted with one of my fluorine chemist friends and he gave me the following reason. Apparently, the fluorine size and electron withdrawing properties result in a chain that has an electronic cloud, without interruption, along its length. He explained it to me as being very silimar to a graphitic structure where the pi electron cloud shields the carbon from any interaction resulting in graphite being a very good lubricant... just like teflon.

He also mentioned that the electronic "sheath" around the carbon gives the carbon chain a helical twist with a period of roughly 23 carbons. He mentioned that some good crystallography discussions were in the literature in the mid to late 60's discussing this helical twist phenomenon.

Interesting...