Surface modification of halogenated polymers: 3. Influence of additives such as alkali cations or nucleophiles on the magnesium reductive treatment of polytetrafluoroethylene

The presence of a small amount of an alkali cation in a magnesium solution dramatically increases the rate of defluorination of PTFE and enhances oxygenation. Evidence of this effect is observed for concentrations down to 1 mM and treatment durations of only 10 s. The presence of the alkali cation also makes the polymer porous. The rate of defluorination and the depth of attack increase both with the alkali cation concentration and with the duration of the treatment. Sodium is more reactive than potassium which is itself more reactive than lithium. The phenomenon is not limited to alkali cations and is also evident with the tetrabutylammonium cation. When nucleophiles such as diethylphosphite, thiophenoxide or the anions of 2-mercaptopyridine and thiourea are present in a solution of magnesium containing a moderate amount of solvated electrons (<50 mM), the grafting of the nucleophile to the polymer occurs but leads to poor yields.