End groups acyl fluoride

Perfluoropolyethers with the linear perfluoropropoxy repeat unit have been commercialized (28). They are prepared by the anionic oligomerization of tetrafluorooxetane followed by direct fluorination to remove the acyl fluoride end group as well as to fluorinate the remaining CH2 groups n can vary widely. 

Synthetic methods have limited the preparation of saturated perfluoropolyethers. The most successful perfluoropolyether synthetic chemistry has been DuPont s anionic polymerization of perfluoroepoxides, particularly hexafluoro-propylene oxide and tetrafluoroethylene oxide (39). Their synthetic procedure is a three-step scheme for saturated perfluoropolyether production involving oxidation of perfluoroolefins to perfluoroepoxides, anionic polymerization to acyl fluoride terminated perfluoropolyethers, and conversion of acyl fluoride end groups to unreactive end groups by decarboxylation reactions or chaincoupling photolytic decarboxylate reactions. 

Hydrolysis of acyl fluoride end groups on hexa-fluoropropylene-tetrafluoroethylene copolymer with 1% water in a corrosion-resistant 28-mm intermeshing twin-screw extruder at 360°C. 

Figure 3 reflects stabilization or end-capping of the reactive acyl fluoride end group, which may be carried out in several ways as shown. Antimony fluoride adds a fluorine atom to the chain while eliminating carbon monoxide ( ). Base treatment of the acyl fluoride gives rise to an additional hydrogen atom, and irradiation approximately doubles the molecular weight with the elimination of two gas species. This last mechanism is utilized in our work. The materials shown in... 

Acyl Fluoride - An end group of polytetrafiuoroeth-ylene polymers commonly present in the polymers after they have been subjected to radiation in the presence of oxygen. 

The HFPO oligomers are acid fluorides and acylate benzene or toluene in the presence of a Friedel-Crafts catalyst such as AICI3 [101,102]. The resulting oligomers with an aryl end group are soluble and exhibit surface activity in toluene and w-xylene [102] ... 

Before attempting polymerization, we performed a model reaction to confirm the difference in the above substituent effects between a monomer and a polymer [16]. We chose 9 as a model of the propagating end, 10 as a model of the acyl group of mmiomer 8, and 11 as a model of the nucleophilic site of 8. When the reaction of 11 with equimolar amounts of 9 and 10 was performed in the presence of fluoride ion at room temperature, 11 reacted selectively with 9 (Scheme 9). The observed selectivity indicated that monomer 8 could undergo CGCP. However, the polymerization of 8 proceeded with concomitant precipitation of polymer, and it was not determined whether CGCP had actually occurred. 

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