Fluorinated heterocyclic polymers

Fluorinated Heterocyclic Polymers for Membrane-Based Applications... 

Fluorinated Heterocyclic Polymers as Proton Exchange Membranes... 

Criss-cross cycloaddition reactions with hexafluoroacetone azine to give partially fluorinated heterocycles and polymers 06H(67)443. gem-Disubstituent effect in formation of heterocycles 05CRV1735. 

Polyazoles, a class of high-strength heterocyclic polymers, are classified into three broad classes depending on the hetero atoms, like PBO, PBI, and PBT. However, their inherent insolubility in common organic solvents restricts their growth in practical applications. Different methods have been applied to enhance their solubility and processability. Incorporation of the fluorinated moiety in the polymer backbone is one of the important ways to improve the solubility and processability. The fluorinated poly azoles obtained... 

With the background theoretical and experimental studies detailed in the previous sections, it is now possible to study structure and bonding in polymer systems which have proved intractable by more conventional techniques. As an interesting example of this, we may consider the identification of a polymer produced in substantial yield as a by-product in the fluoride ion initiated reaction of hexaf1uorobut-2-yne with fluorinated heterocyclic molecules. The reaction produces substantial amounts of an... 

As well as phenyl derivatives, other products have been prepared by hydrolysis of alkoxysilanes such as cyclohexenyl or naphthyl derivatives as well as heterocyclic compounds based on thienyl rings (Table 31, entries 28-33). Few practical applications have been reported for this type of compound, except for the styryl compound T81C6H4-A-CFI = CH2]s, and the fluorinated TslCeFsJs which have been used in polymer blending (Table 31, entries 13 and 28). ... 

Dioxathiolane 2,2-dioxides (cyclic sulfate esters of 1,2-diols) are used in practice like sultones to introduce acid substituents into nitrogen heterocycles (48BSF1002), especially into cyanine dyes (58GEP1028718). Fluorinated derivatives are useful in the treatment of textiles such as cotton to impart wash and wear characteristics (62USP3055913). The conversion of cyclic sulfates into resinous film-forming polymers has been likewise patented (64USP3154526). 

All three commercial amorphous fluoropolymers. Teflon AF, Hyflon AD, and Cytop posses a unique set of properties. All dissolve in fluorinated solvents and thus may be spin coated to produce thin hlms and coatings. The polymers may also be extruded and molded using traditional polymer processing techniques. Note that the polymers are not soluble in hydrocarbon solvents or water and retain the chemical and thermal stability of perfluorinated polymers such as Teflon . These polymers have lower density than the well-known semicrystalline perfluorinated polymers such as pTFE that results in lower refractive index, lower thermal conductivity, higher gas permeability, and lower dielectric constant. The polymers are transparent and have excellent mechanical properties below their Tg due to their amorphous character. The presence of a heterocyclic ring in the polymer backbone of these materials is key... 

The future will see many more applications of fluorine-containing heterocycles. The bulk of these applications will be considered as building blocks to add fluorine to primarily hydrocarbon molecules and polymers to utilize the unique and desired properties that relatively small amounts of fluorine can provide. 

Oxadiazoles experienced an almost 80-year long period of scientific lethargy before they tickled the curiosity of chemists. The study of chemical and photochemical reactivity of 1,2,4-oxadiazoles opened the way to a series of applications in heterocyclic synthesis. Today, 1,2,4-oxadiazoles are known in medicinal chemistry for their use as bioisosters of esters and amides. Furthermore, fluorinated 1,2,4-oxadiazoles have been applied in materials science either by themselves or for the targeted modification of polymers and macromolecules. Overall, the synthesis of... 

S.K. Sen, B. Dasgupta, S. Banerjee, Effect of introduction of heterocyclic moieties into polymer backbone on gas transport properties of fluorinated poly (ether imide) membranes,... 

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. 

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