Novel Generation of Teflon® Under Ambient Conditions

Felicia Taw, Postdoc Pub Prize

Polytetrafluoroethylene (PTFE, commonly known as Teflon®), along with other related fluorinated polymers (e.g., Kel-F or Viton) are currently produced under high pressures using radical-based chemical processes, which allow little control over polymer microstructure.  On the contrary, hydrocarbon-based polymers (e.g., polyethylene or polystyrene) with finely-tuned properties can be accessed by utilizing a wide variety of transition-metal polymerization catalysts.  Thus, there is a need to develop analogous transition-metal catalytic platforms that can polymerize fluorinated olefins with a high degree of control over polymer structure.

The discovery of new transition-metal perfluoroalkyl complexes and progress toward an understanding of their behavior are crucial steps in this direction.  We have synthesized the first early transition-metal perfluoroalkyl complexes, Cp2Ti(CF3)(X) [X = F, Cl, Br, I, OSO2CF3, OSO2Ph, and N3].

These complexes were previously believed to be unattainable due to their high propensity to undergo α-fluoride elimination and subsequent decomposition.  However, several of these titanium perfluoroalkyl compounds have now been characterized by single-crystal X-ray diffraction studies, and the Ti-CF3 linkage in these complexes is remarkably robust and shows no evidence of an α-fluoride interaction (Ti···F-CF2) between the electrophilic Ti(IV) metal center and any of the C-F bonds in the trifluoromethyl group.

The titanium trifluoromethyl fluoride complex, Cp2Ti(CF3)(F), is quite stable when cold (< 0 °C) but becomes a shock-sensitive compound at room temperature.  The products of decomposition can be deposited as a film and imaged using Scanning Electron Microscopy.  Formation of spherical nanoparticles on the order of 100 nm is observed, and preliminary evidence indicates that these films are comprised of Teflon® in addition to other fluorinated materials.

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