Fluorinated poly substitution

Reactions of perfluorinated alkenes, such as hexafluoropropene, with fluoride ion give perfluoroalkylcarbanions which can act as nucleophiles in S Ar reactions with perfluoroheteroaromatic systems (Fig. 8.13). These reactions are another example of mirror-image chemistry and reflect well-known Friedel-Crafts reactions of hydrocarbon systems that proceed by reaction of the corresponding electrophile and carbocationic intermediates. Poly substitution processes are possible and, indeed, all five fluorine atoms may be replaced upon reaction with an excess of tetrafluoroethylene and fluoride ion. ... 

Song et al. [72] synthesized fluorinated poly(phthalazinone ether)s (FPPEs) via a modified nucleophilic aromatic substitution using mild reaction conditions. Potassium fluoride and calcium hydride were used as the catalyst and base in preparing highly... 

Kim et al. prepared highly fluorinated poly(arylene ether sulfone) [88] containing an ethynyl end group as thermal cross-linkable groups (Scheme 2.24) via nucleophilic aromatic substitution from 6F-BPA or 4,4 -(trifluoromethylphenylisopropylidene) diphenol (3FBPA) with an excess of pentafluorophenyl sulfone, followed by reaction with 3-ethylnylphenol, studied the effect of reaction temperature and time. 

Tao et al. prepared fluorinated polyimide (3-86 in Table 3.4) [126], from multi-trifluoromethyl-substituted diamine, which had a dielectric constant as low as 2.49. The dielectric constants decreased gradually with an increase in fluorene loading. The dielectric constant value was not only much lower than non-fluorinated polyimides such as PMDA-ODA (3.16) [127], it was also lower than some of the fluorinated polyimides such as those derived from 3,3, 5,5 -tetrafluoro-4,4 -diaminodiphenylmethane (TFDAM) and dianhydrides (2.73-2.82) [128] and from a,a-fcA(4-amino-3,5-difluorophenyl)phenyl-methane (4FMA) and dianhydrides (2.60-2.83) [129]. Wang et al. [130] prepared fluorinated poly-iinides (3-87 in Table 3.4) by incorporating diisopropyl-substituted fluorene moieties, which led to an improvement in solubility and dielectric properties. The dielectric constant obtained with the... 

Maruyama et al. prepared a series of novel fluorinated poly(o-hydroxy amides) of high molecular weights (Mw = 3100 and M =2100g/ mol) by the low-temperature solution polycondensation of tri-methylsilyl substituted 2,2-bis... 

Hilborn et al. demonstrated the synthesis of PBOs (Figure 5.29) by polymerization of bis(fluorophenyl benzoxazoles) with bisphenols. This polymerization was based on the activation of the fluoro group toward nucleophilic aromatic substitution by the oxazole component of the benzoxazole heterocyclic [51]. The TgS of the poly(arylene ether benzoxazoles) ranged from 213 to 303 °C, depending on the bisphenol and activated dihalide used in the synthesis. Generally, the TgS increased with the bulkiness of the bisphenol used. The polymers containing the >C(CF3)2 unit in both the benzoxazole and the bisphenol moiety in the monomers showed higher solubility (NMP) compared to the other PBOs. The physical properties of fluorinated poly(arylene ether benzoxazole) s are presented in Table 5.3. 

Poly(TSE-co-4FS) Copolymers Copolymerization of fluorine ring substituted 2-phenyl-1,1-dicyanoethene (TSE) with 4-fluorostyrene (4FST) was prepared from an equimolar monomer feed composition in the presence of a 1,1 -Azobis(cyclohexanecarbonitrile) (ABCN) as the radical initiator [88]. The yield was close to 59% (Scheme 20.7). Homopolymerization of 4FST was conducted under identical conditions as those in the copolymerization (Yield = 76%). 

Chen Z, Zhu J, Xie H, Li S, Wu Y, Gong Y (2011) Selective synthesis of poly-substituted fluorine-containing pyridines and dihydropyrimidines via cascade C-F bond cleavage protocol. Org Biomol Chem 9 5682-5691... 

In 2006, McGrath and coworkers reported multiblock sulfonated-fluorinated poly(arylene ether sulfone)s (MB) for PEMs by the nucleophilic aromatic substitution of the dialkali metal salt of bisphenol-terminated poly(arylene ether sulfone) and decafluorobiphenyl-terminated poly(arylene ether) [28] (Scheme 4.10). 

The presence of carbon—fluorine bonds in organic polymers is known to characteristically impart polymer stabiUty and solvent resistance. The poly(fluorosibcones) are siloxane polymers with fluorinated organic substituents bonded to siUcon. Poly(fluorosibcones) have unique appHcations resulting from the combination provided by fluorine substitution into a siloxane polymer stmcture (see Silicon compounds, silicones). 

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

This polymer is the completely fluorine-substituted analogue of poly(ethylene) i.e. [CF2CF2—The amount of this polymer produced commercially is very small compared with the output of many other synthetic polymers, but it has a number of important specialised uses and so is worth considering briefly. 

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]. 

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. 

Poly(Fluoroalkoxyphosphazene) Elastomers. When I is substituted with a mixture of trifluoroethoxide and telomer fluoroalkoxides, an elastomer II is obtained having a fluorine content of approximately 55 percent. A small amount of an unsaturated cure site may also be Incorporated into the polymer to promote vulcanization. 

R.M. Gurge, A.M. Sarker, P.M. Lahti, B. Hu, and F.E. Karasz, Light emitting properties of fluorine-substituted poly(l,4-phenylene vinylenes), Macromolecules, 30 8286-8292, 1997. 

R. Riehn, J. Morgado, R. Iqbal, S.C. Moratti, A.B. Holmes, S. Volta, and F. Cacialli, Fluorine substituted poly(p-phenylene vinylenes) copolymers, Synth. Met., 124 67-69, 2001. 

Crystallinity of these hexafluoroisopropylidene-unit-containing poly(ketone)s is low except for poly(sulfide ketone) (13). The water contact angle for the fluorine-containing poly(ketone) films is high, being 98° for poly(ether ketone) (11), from 2,2-bis(4-carboxyphenyl)-l,l, l,3,3,3-hexafluoropropane(15) and 96° for poly(sulfide ketone) (13) from 15, whereas it is 78° for poly(ether ketone) from 2,2-bis(4-carboxy-phenyl)propane (16) and 74° for the poly(sulfide ketone) from 16. This result indicates that the substitution of isopropylidene units of poly-(ketone)s with hexafluoroisopropylidene units has a remarkable effect on the surface properties of poly(ketone) films. 

The incorporation of fluorine atoms improves the solubility of aromatic condensation polymers without causing them to lose their high thermal stability and modifies the processability. Hexafluoroisopropylidene-unit-containing poly-(azomethine)s and copoly(azomethine)s are readily soluble in highly polar solvents such as DMAc, HMPA, and NMP, and they also dissolve completely in dichloromethane, chloroform, and THF, whereas poly(azomethine)s derived from 21 and 22 and having no fluorine atom are insoluble in these solvents.20 Accordingly, the solubility of aromatic poly(azomethine)s is remarkably improved by substituting isopropylidene units with fluorine atoms. 

Mamyama et al.25 have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A,A 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoro-propane (25) with aromatic diacids and subsequent thermal cyclodehydration of the resulting poly(o-hydroxy amide)s in vacuo. In this method, aromatic diamines with low nucleophilicity are activated more positively through the conversion to the /V-silylated diamines, and the nucleophilicity of the fluorine-containing bis(o-aminophenol) can be improved by silylation. 

Cycloalkyl and secondary alkyl bromides react with N02 BF4 in pyridinium poly(hydrogen fluoride) solution to yield /J-fluorinated compounds in moderate to good yields. In the case of the cyclic starting materials like 1-bromocyclohexane only trans-substituted products are formed (see Table 22). 

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