Which of the following is fully fluorinated polymer?

The term “fully fluorinated polymer” means that every hydrogen present in the parent hydrocarbon monomer has been replaced by fluorine atoms in the polymer chain.

For an ethylene-type backbone, complete fluorination converts $$CH_2=CH_2$$ to $$F_2C=CF_2$$. Polymerisation of $$F_2C=CF_2$$ (tetrafluoroethylene) gives polytetrafluoroethylene (PTFE), commonly called Teflon:

$$\;n\,F_2C=CF_2 \;\longrightarrow\; (-CF_2-CF_2-)_n$$

In this structure every carbon is bonded only to fluorine and carbon; no hydrogen (or any other heteroatom) remains. Hence PTFE/Teflon is a fully fluorinated polymer.

Now examine the other choices:

Option A - Neoprene: polymer of chloroprene, $$(-CH_2-C(Cl)=CH-CH_2-)_n$$, contains both chlorine and hydrogen, so it is not fully fluorinated.

Option C - Thiokol: polysulfide rubber formed from ethylene dichloride and sodium polysulfide, contains sulfur as well as hydrogen; again, not fluorinated.

Option D - PFC: generally refers to phenol-formaldehyde condensate (Bakelite) or perfluorocarbons (depending on context). In polymer science examinations, PFC is taken as phenol-formaldehyde resin, which clearly contains oxygen and hydrogen, so it is not fully fluorinated.

Thus, the only polymer in the list with every hydrogen replaced by fluorine is Teflon.

Final answer: Option B which is: Teflon