Aromatic fluoropolymers

In recent years, considerable attention hcis been devoted to the preparation of fluorine-containing polymers due to their unique properties and high-temperature performance. The incorporation of fluorine atoms (or groups containing fluorine atoms) into polymer chains changes solubility of polymers, glass transition temperature (T ) and thermal stability, while also led to decreased moisture absorption and dielectric constant. The aromatic fluoropolymers have currently been used as films, coatings microelectronics devices [37,55-60]. 

These include anionic polymerizations of some conjugated monomers such as -tri-fluoromethyl acrylates, fluorostyrene derivatives and 1,4-perfluoro-butadiene (17), and condensation polymerization to afford such aromatic fluoropolymers as polyarylates and aramides (18). In addition, fluorinated polyimides are on a way of evaluation for practical applications in the electronics field. 

This section seeks to report the preparation and characterization of PEMs based on partially fluorinated aromatic polymers. In the past few decades, attention has focused on the preparation of new fluorinated monomers and aromatic fluoropolymers. This topic was recently reviewed [70], summarizing the characteristic effects of the aromatic group on the physicochemical properties (e.g., Tg and the thermostability of the obtained polymers). 

One of the first fictional fluoropolymers was poly-1,2,2-trifluorostyrene. On one hand, it has much better oxidation and chemical resistance in comparison with common hydrocarbon polymers and, on the other hand, a wide range of functional groups can be attached to the aromatic ring. A sulfonated polymer was successfully used as a membrane for fuel cells by General Electric Co.3... 

Ford, L. A., DesMarteau, D. D. and Smith, D. W., Jr. 2005. Perfluorocyclobutyl (PFCB) aromatic polyethers Synthesis and characterization of new sulfonamide containing monomers and fluoropolymers. Journal of Fluorine Chemistry 126 653-660. 

Third 1965 PPS, polyimides, aromatic polyesters, aromatic polyamides, fluoropolymers, thermoplastic elastomers High mechanical strength, very high melting point, superior chemical resistance... 

Compared to fluoropolymers, aliphatic and aromatic polymers are less hydrophobic, and the sulfonic acid functional group is less acidic and less polar. Nafion is a superacid, with a piCa -6 as estimated using pJCa database 4.0 [130]. Ma et al. [131] determined the pKa of Nafion 117 and the sulfonated aromatic polymer, BPSH (Scheme 3b), to be -3.09 and -2.04, respectively, while the simplest aromatic sulfonic acid, benzene sulfonic acid, has a pJCa of 0.70 [132]. Aromatic polymers are more rigid than Nafion and possess shorter ionic side chains, and therefore are expected to exhibit a lesser degree of separation between hydrophilic and hydrophobic domains. SAXS measurements on rigid aromatic polymers, such as SPIs based on naphthalenic dianhydride (Scheme 3k, x = 5, xly = 30/70) indicate the ab-... 

As described previously, Nafion membranes exhibit much higher proton conductivity than any other aliphatic and aromatic PEMs bearing similar ion content due to the special chemical structure and morphology. Partially sul-fonated polystyrene (SPS) and PTFSSA have the same backbone except PTF-SSA possesses a fluoropolymer backbone. The dependence of proton conductivity on EW for SPS at 22 °C [172] and PTFSSA [138] membranes is shown in Fig. 17. The conductivities of the fluorinated block copolymer P(VDF-co-... 

The reaction of polymers with oxygen becomes less probable with decreasing polymer hydrogen content. Thus, fluoropolymers have higher thermal stabilities than nonfluorinated polymers with otherwise the same constitution. Aromatic and heteroaromatic substituents are even more thermally resistant. 

D.W. Smith Jr., D.A. Babb, Perfluorocy-clobutane aromatic polyethers. Synthesis and characterization of new siloxane-containing fluoropolymers. Macromolecules 29 (3) (1996) 852-860. 

Engineering thermoplastic resins (ETP) are those whose set of properties (mechanical, thermal, chemical) allows them to be used in engineering applications. They are more expensive than commodity thermoplastics and generally include polyamides (PA), polycarbonate (PC), linear polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyphenylene ether (PPE) and polyoxymethylene (POM). Specialty resins show more specialized performance, often in terms of a continuous service temperature of 200°C or more and are significantly more expensive than engineering resins. This family include fluoropolymers, liquid crystal polymers (LCP), polyphenylene sulfide (PPS), aromatic polyamides (PARA), polysulfones (P ), polyimides and polyetherimides. 

Fluoropolymer processing aid concentrates can be analysed by FTIR to within 0.1% within a few min [85]. Letdown processing aid levels can be determined down to approximately 400 to 500 ppm with an accuracy of 50 ppm. It is not envisaged that FTIR will be a suitable means for analysing tracers for ownership (of defective products). Low concentrations are necessary here in order not to upset materials properties and to avoid confusion with the additive package. This rules out many aromatics, S and P compounds. Si-based materials. Cl and Br compounds, elements found in colourants (Ti, Ba, Ca, etc.) as well as other elements (e.g. Zn) and various functional groups (COOH, etc.). 

Although the crossUnking mechanism of amines and diamines onto VDF-based fluoropolymers proceed in three main steps and are similar, the reaction conditions (temperature and time) and the physical properties of aliphatic and aromatic containing mono or diamines are different. 

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