Fluorinated phosphazene

Table 9 General characteristics of fluorinated phosphazene polymers and copolymers ...

Ultramark 1621, a mixture of fluorinated phosphazenes, was proposed as a reference compound for calibration in the range of m/z 800 to 2000 [28]. It was also recommended for ion-trap instmments from Thermo Finnigan. Ultramaik 1621 strongly adsorbs to surfaces and is difficnlt to remove due to its poor solubility in common solvents [30]. A proprietary mixtnre of fluorinated phosphazenes is recommended as reference compound by Agilent Technologies. Water cluster ions have been proposed for calibration up to m/z 3000 [31]. 

Rollins HW, Harrup MK, Dufek EJ, Jamison DK, Sazhin SV, Gering KL, Daubaras DL (2014) Fluorinated phosphazene co-solvents for improved thermal and safety performance in lithium-ion battery electrolytes. J Power Sources 263 66-74. doi 10.1016/j.jpowsour.2014. 04.015... 

Other studies on the flame retardant applications of phosphazene derivatives include the use of cyclotriphosphazenes to improve the flame-retardant properties of epojy composites,using fluorinated phosphazene derivatives as non-flammable electrolytes in lithium ion batteries and utilizing phosphazenes as flame-retardant additives in curing polysiloxanes. °... 

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]. 

Phosphazene polymers can act as biomaterials in several different ways [401, 402,407]. What is important in the consideration of skeletal properties is that the -P=N- backbone can be considered as an extremely stable substrate when fluorinated alcohols [399,457] or phenoxy [172] substituents are used in the substitution process of the chlorine atoms of (NPCl2)n> but it becomes highly hydrolytically unstable when simple amino acid [464] or imidazole [405-407] derivatives are attached to the phosphorus. In this case, an extraordinary demolition reaction of the polymer chain takes place under mild hydrolytic conditions transforming skeletal nitrogen and phosphorus into ammonium salts and phosphates, respectively [405-407,464]. This opens wide perspectives in biomedical sciences for the utilization of these materials, for instance, as drug delivery systems [213,401,405,406,464] and bioerodible substrates [403,404]. 

As reported in Table 5 and in other recent publications [399,491 ], polymers with very low Tg are expected when the inherent skeletal flexibihty of poly-phosphazenes is coupled with fluorinated alcohols of low dimensions and/or of high chain mobility. In fact, the Tg values for POPs substituted with fluorinated alcohols vary between -50 °C and -90 °C, confirming the extreme chain mobility of these polymers and the existence in them of very low torsional energy barriers. 

When x=l and y=2,3,4,. and Z=H or F, a new class of polyphosphazene substrates is obtained, which derive from the simultaneous substitution of two different fluorinated alcohols of different lengths on the same polydichloro-phosphazene macromolecule. The general structure of the substrates is reported below. 

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). 

Fluorination of ClsP NMe-BCls (Section 2) by arsenic trifluoride results in the formation the well-characterized dimeric phosphazene (23) ... 

The incorporation of polar groups in unvulcanized polymers reduces their solubility in benzene. Thus the copolymer of acrylonitrile and butadiene (NBR), polychlorobutadiene (Neoprene), and fluorinated EP (the copolymer of ethylene and propylene) are less soluble in benzene and lubricating oils than the previously cited elastomers. Likewise, silicones and phosphazene elastomers, as well as elastomeric polyfluorocarbons, are insoluble in many oils and aromatic hydrocarbons because of their extremely low solubility parameters (silicons 7-8 H polytetrafluoroethylene 6.2 benzene 9.2 toluene 8.9 pine oil P.6). 

Figure 3.7 P NMR spectra of cyclic trimeric and high polymeric phenyl-fluoro phosphazenes. Note (1) the shift in the whole spectrum that occurs in moving from a cyclic small-molecule phosphazene to a related high polymer, and (2) the chemical shift and splitting pattern that results from phosphorus coupling to the two fluorine atoms or to one fluorine. Spectra provided by W. D. Coggio.

For example, there is considerable interest in the preparation of sulfur-nitrogen polymers that have organic substituents on the sulfur atoms.56 This could help alleviate the intractability problem mentioned, and could also give rise to a series of polymers that parallel the phosphazenes in their structural variability. A series of polymers with S-N backbones of this type has been prepared, but with oxygen atoms as some of the substituents. The basic structure has the repeat unit -RS(=0)(N)- or -FS(=0)(N)-but they have not yet been studied in detail. The fluorine-containing polymer, however, is known to be a tough elastomer which is unaffected by water, acids, or bases up to 100 °C.7... 

Two other families of polymers with fluorinated side groups have been investigated in the field of elastomers polysiloxanes and polyphosphazenes [394, 395]. These latter macromolecules, called NPF, have been obtained by chemical change of poly(dichlorophosphazene) as for classic phosphazenes ... 

A great deal of basicity data is available on substituted chlorophosphazenes. None has hitherto been published on fluoro-phosphazenes. A priori, one surmises a greater electron-withdrawing inductive effect for fluorine, which oould be compensated for by the greater potential of fluorine to back-donate by a mesomsric effect. Data is new compared on structurally related chloro- and... 

The electron-withdrawing ability of the fluorine atom can draw electron density from an adjacent nitrogen atom, making a distant nitrogen more basic. A second effect is the shortening of the P—Cl bond in a P(F)C1 vs. a PCI2 center (32). Thus, an incoming Lewis acid will interact with the phosphazene at a site that is distant from the P(F)C1 site. 

Two commercial phosphazene elastomers were developed and marketed in the mid-1980s, namely, poly(fluoroalkoxyphosphazene) elastomer (ASTM International designation FZ) and poly(aryloxyphosphazene) elastomer (ASTM International designation PZ) [109]. The structure of the fluorinated product is as follows [110] ... 

A solution of 17.2 g (0.38 mole) of anhydrous dimethylamine in dry diethyl ether (SO mL) is added from a pressure-equalizing dropping funnel over 30 minutes to a well-stirred solution of 22.2 g (0.064 mole) of hexachlorocyclotri-phosphazene in 750 mL of diethyl ether contained in a 1-L, three-necked flask cooled to -78°. The solution is then allowed to warm slowly overnight to room temperature when the precipitated amine hydrochloride is filtered and washed with diethyl ether. After removal of the solvent from the combined filtrate and washings, the material remaining is recrystallized from light petroleum ether (68-80° fraction). On careful fractionation the pure rrons-isomer (mp 105°) can be obtained as the first fraction (13.6 g), but subsequent fractions are mixtures of the cis- and /rans-isomers. Such mixtures, however, are acceptable for the fluorination described in Section B. 

O4CSFS, Cesium fluorine sulfate, 24 22 04Fi2N3P3C,oHi4, Poly[2,2-dimethyl-4,4,6,6-tetrakis(2,2,2-trifluoroethoxy)catenatri-phosphazene-l,6-diyl], 25 67 04F,2N3P3SiCi3H22, Poly[2-methyl-4,4,6,6-tetrakise(2,2,2-trifluoroethoxy)-2-[(tri-methylsilyl)methyl]catenatriphospha-zene-l,6-diyl], 25 64... 

In the case of the reaction with aryloxides, only substitution of the P-Cl bonds can be achieved even after prolonged reaction times. Interestingly, the sulfur-chlorine (in 19) or sulfur-fluorine (in 21) bonds remain intact. This regioselec-tive substitution pattern is exactly the opposite to that observed with polythio-phosphazenes 12 which contain sulfur(IV) centers where perhalogenated derivatives substitute with aryloxides preferentially at sulfur [38]. In contrast to aryloxides, amines readily substitute at both the phosphorus and sulfur sites at ambient temperature. The resulting moisture stable polythionyiphosphazenes range from colorless elastomeric materials (see Fig. 2) to glassy polymers which are isolated as white powders (see Table 1). 

In 1958 I gave a course of lectures on aromatic character in Coulson s Theoretical Summer School in Oxford. After one of them I met Norman Paddock (later Professor on Chemistry in the University of British Columbia), then working in the research department of Albright and Wilson. The company s commercial interests included the cyclic phosphonitrilic halides (phosphazenes) that Paddock was characterizing. They have ring systems with alternate nitrogen and phosphorus atoms. The substituents on the pentavalent phosphorus atoms may be chlorines or fluorines or other atoms or groups. 

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