Perfluorinated alkoxy

The macromolecule of perfluorinated alkoxy (PFA) or simply perfluoroalkoxy is based on the monomer unit [—(CFj) —CF(0—C F, )—(CFj) —] . Perfluoroalkoxy is similar to other fluorocarbons such as polytetrafluoroethylene and fluorinated ethylene propylene regarding its chemical resistance, dielectric properties, and coefficient of friction. Its mechanical strength. Shore hardness, and wear resistance are similar to PTFE and superior to that of FEP at temperatures above ISO C. PFA has a good heat resistance from -200 C up to 260°C near to that of PTFE but having a better creep resistance. 

Scheme 40 Synthesis of porphyrazines with perfluorinated alkoxy and aryloxy groups...

Examples of replacement of fluorine in saturated aliphatic perfluorinated compounds by alkoxy and aryloxy groups are relatively scarce since such fluorine atoms are generally inert toward nucleophiles in SN2 reactions. 

HFPO is reacted with a perfluorinated acylfluoride to produce perfluoro-2-alkoxy-propionyl fluoride ... 

NMR studies it has been observed that the long molecular axis is nearly parallel to the para- x s of the phenyl moiety and hence the first few fragments of the chain attached to the indazole group are not along this axis. This requires that the alkoxy chain attached to the indazole group has at least six carbon atoms to promote liquid crystalline behaviour. The order parameters of 4 -cyanophenyl 4-heptylbenzoate have been obtained by using 2D-NMR spectroscopy.Linear relationships between C-chemical shifts and order parameters have been obtained. Phase behaviour of a mixture of this liquid crystal and its chain-perfluorinated analogue has also been studied. 

There are two distinct families of fluoropolymers perfluorinated (like PTFE) and the partially fluori-nated (like PVDF) polymers. The major types that are rotationally molded are polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene (ETFE), ethyl-ene-chlorotrifluoroethylene (EC IFF), andperfluoro-alkoxy (PFA). 

---