Trifluoroethoxy

Applications. Among the P—O- and P—N-substituted polymers, the fluoroalkoxy- and aryloxy-substituted polymers have so far shown the greatest commercial promise (14—16). Both poly[bis(2,2,2-trifluoroethoxy)phosphazene] [27290-40-0] and poly(diphenoxyphosphazene) [28212-48-8] are microcrystalline, thermoplastic polymers. However, when the substituent symmetry is dismpted with a randomly placed second substituent of different length, the polymers become amorphous and serve as good elastomers. Following initial development of the fluorophosphazene elastomers by the Firestone Tire and Rubber Co., both the fluoroalkoxy (EYPEL-F) and aryloxy (EYPEL-A) elastomers were manufactured by the Ethyl Corp. in the United States from the mid-1980s until 1993 (see ELASTOLffiRS,SYNTHETic-PHOSPHAZENEs). 

Roughly 65% of the substituents are trifluoroethoxy, and 35% are telomer alcohols prepared from tetrafluoroethylene and methanol. About 0.5 mol % of an aHyhc substituent is used as a cross-link site. The substituent pattern is beUeved to be stricdy statistical. 

Figure 12.30 Potential uses of polyphosphazenes (a) A thin film of a poly(aminophosphazene) sueh materials are of interest for biomedical applications, (b) Fibres of poly[bis(trifluoroethoxy)phosphazene] these fibres are water-repellant, resistant to hydrolysis or strong sunlight, and do not burn, (c) Cotton cloth treated with a poly(fluoroalkoxyphosphazene) showing the water repellaney eonferred by the phosphazene. (d) Polyphosphazene elastomers are now being manufaetured for use in fuel lines, gaskets, O-rings, shock absorbers, and carburettor eomponents they are impervious to oils and fuels, do not bum, and remain flexible at very low temperatures. Photographs by eourtesy of H. R. Allcock (Pennsylvania State University) and the Firestone Tire and Rubber Company.

Tile same methodology as mentioned for the preparation of (9) was applied for the synthesis of 8-nitro-l,6-naphthyridines. Heating diethyl N- 3-nitropyridin-4-yl)aminomethylenemalonate (12) in diphenyl ether yields ethyl 8-nitro-l,6-naphthyridin-4(lH)-one 3-carboxylate (13) (63JCS4237, 30%) and acid treatment of 4-( y, y-diethoxypropylamino)-5-nitro-2-(/3,/3 -trifluoroethoxy)-pyridine (14) gives in a similar way 8-nitro-5-(/3, /3-triflu-oroethoxy)-l,2-dihydro-l,6-naphthyridine (15, 76%). Subsequent oxidation with chloranil, acid hydrolysis, and methylation with methyl iodide gives 8-nitro-6-methyl-l,6-naphthyridin-5(6H)-one (16,63%) (81JHC941). 

Reduction of 8-nitro-5-(/3,/3,/3-trifluoroethoxy)-l,6-naphthyridine (141) afforded the corresponding 8-amino compound (142, 45%) (81JHC941). 

Chemical Name N-(2-Piperidylmethyl)-2,5-bis(2,2,2-trifluoroethoxy)benzamide Common Name —... 

After 2 hours the mixture is cooled to about 0°C and the crude product Is collected by filtration, washed with diethyl ether and dried in a vacuum oven. After treatment with decolorizing charcoal and recrystallization from an equivolume mixture of isopropanol and methanol, the product, 2,5-bis(2,2,2-trifluoroethoxy)-N-(2-piperidylmethyl)benzamide hydrochloride has a MP of 228°C to 229°C. 

The same procedure has been employed to increase the hydrophobic character of cellulose, by introducing fluorine-containing groups, e.g., 2,2-difluoroethoxy 2,2,2-trifluoroethoxy and octafluoropentoxy. Incorporation of hydrophobic moieties into cellulose is expected to increase the polymer compatibility with other materials, e.g., synthetic polymers. Note that an important part of incompatibility is due to the highly hydrophilic character of cellulose. Decreasing this character is expected to affect Tg of the derivative, as shown by cellulose propionate/octafluoropentoxy acetate (total DS = 3.0, partial DS in each moiety = 1.5), whose Tg is only 53 °C. The products are more stable than their fluorine-free counterparts, and the terminal CF2 - H group affects Tg much less than OH-substituted trifluoroethoxy celMose derivatives [196,197]. 

CN 2-[[[3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridinyl]methyl]sulfinyl]-l//-benzimidazole... 

As can be seen, the first example of phosphoranimine polymerization process was proposed by E. P. Flindt and H. Rose [314] in 1977 for tris(trifluoroethoxy)-AT-(trimethylsilyl)phosphoranimine, which could be polymerized to poly[bis-(trifiuoroethoxy)phosphazene] (MW 4000-10,000) by simple heating at 200 °C. 

The phosphazene backbone has a particularly high resistance to thermal treatment and to homolytic scission of the -P=N- bonds, possibly due to the combination of the high strength of the phosphazene bond and its remarkable ionic character [456]. As a consequence, the onset of thermal decomposition phenomena (as detected, for instance, by TGA) are observed at considerably high temperatures for poly[bis(trifluoroethoxy)phosphazene], [NP(OCH2CF3)2]n [391, 399, 457], for phosphazene copolymers substituted with fluorinated alcohols of different length [391, 399, 457], for polyspirophosphazenes substituted with 2,2 -dihydroxybiphenyl groups [458], and for poly(alkyl/aryl)-phosphazenes [332]. 

S. H. Rose in 1968 [263, 265] first described the reaction of polydichloro-phosphazene with trifluoroethoxy groups coupled with a second fluorinated alkoxy residue of longer chain. During the successive twenty years they were deeply investigated by Horizon Inc. [263, 265, 502-506, 518, 544, 552-554], AMMRC [396, 452, 555-557], NASA [517, 522, 523], The Firestone Tire and Rubber [393,519,528,530,533,558,559], and Ethyl Co. [507,560,561] for the applications described above (vide supra). 

The same fluoroalkoxy substituents, however, are able to enhance substitutional reactivity of fluorinated polyphosphazenes by originating methatetical exchange reactions on polymers in the presence of new nucleophiles and under appropriate experimental conditions. Thus, a series of exchange reactions at phosphorus atoms bearing the trifluoroethoxy substituents in PTFEP have been describedbyH.R. Allcock [508] (Fig. 13),Cowie [482,483] (Fig. 14), and Ferrar [509] (Fig. 15), while surface modification of PTFEP films were reported by Allcock [514,515] (Fig. 16 or 17) and by Lora [516] (Fig. 18). 

Polyphosphazenes bearing crown ethers (12-crown-4,15-crown-5 and 18-crown-6) as single or as mixed substituents with trifluoroethoxy or methoxy-ethoxyethoxy groups were synthesized by Cowie [601,602] and Allcock [484] and their conductivity studied because it was shown that the incorporation of crown ether molecules into a polymer electrolyte could increase their ionic conductivity. In these macromolecules, the crown ether units were linked to the backbone through oxymethylene spacer groups. 

Additional polyphosphazene hydrogels deal with polymers in which gluco-syl side groups are co-substituted with trifluoroethoxy, phenoxy, methylamino or methoxyethoxyethoxy moieties [646]. 

The first example deals with poly[bis(trifluoroethoxy)phosphazene],PTFEP, film, whose surface is intrinsically hydrophobic but can be converted to hydrophilic by the action of NaOH in dioxane at 80 °C in the presence of tetrabutyl-ammonium bromide [514,515], or by metathetical exchange of trifluoroethoxy moieties with variable types of alkoxides groups [482,483,515] (vide supra). 

Spectral Transparence Starting from 230 nm OCH2CF3 Trifluoroethoxy, 0- Phenoxy or OCH2CH3 Ethoxy Spectral Transparence in the UV range Inertness upon Long Wavelength Irradiation Photocrosslinldng Phenomena in Solid State ... 

Trifluoroethoxy and phenoxy groups are hydrophobic. The methylamino group is hydrophilic. Studies have been made of the effect on surface properties and semipermeabiUty of variations in... 

Allcock, H. R., Schmutz, J. L., and Kosydar, K. M., A new route for poly(organophosphazene) synthesis. Polymerization, copolymerization, and ring-ring equiUbration of trifluoroethoxy-and chloro-substituted cyclotriphosphazenes, Macromolecules. 

The sulphur-bridged pentaoxyphosphorane (41) has been prepared by the route shown and its ground state structure studied by a combination of 1H, l9F, 31P and 15C n.m.r. spectroscopy35. The 19F n.m.r. data indicate that at -65°C (wnere three 19F triplets are observed) the phosphorane exists as structure (42) whereas at 26°C the spectrum (two 19F triplets, ratio 2 1) is consistent with conventional pseudorotation in a monocyclic system at 110°C the three trifluoroethoxy groups become equivalent. 

Figure 6. General structure for phosphazenes with mesogenic side groups. Example is a mixed substituent polymer (VII) where R represents the trifluoroethoxy group and the mesogen with flexible spacer is represented by the curlicue and rectangular box.

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