Fluoropolymers functional groups

Since PTFE was first synthesized more than 50 years ago, fluoropolymers have been produced by radical polymerization and copolymerizaton processes, but without any functional groups, for several reasons. First, the synthesis of functional vinyl compounds suitable for radical polymerization is much more complicated and expensive in comparison with common fluoroolefins. In radical polymerization of one of the simplest possible candidates—perfluorovinyl sulfonic acid (or sulfonyl fluoride—there was not enough reactivity to provide high-molecular-weight polymers or even perfluorinated copolymers with considerable functional comonomer content. Several methods for the synthesis of the other simplest monomer—trifluoroacrylic acid or its esters—were reported,1 but convenient improved synthesis of these compounds as well as radical copolymerization with TFE induced by y-irradiation were not described until 1980.2... 

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... 

From this point of view attaching of functional groups to common inexpensive fluoropolymers seemed to be a very attractive way to improve the chemical and thermal stability of the final functional polymer materials in comparison with common hydrocarbon functional polymers, while keeping the costs quite reason-... 

Fluorinated Polymers with Functional Groups Synthesis and Applications. Langmuir-Blodgett Films from Functional Fluoropolymers... 

Telechelic (or a, co-difunctional) oligomers exhibit functional groups at both ends of the oligomeric backbone. These compounds are quite useful precursors for well defined architectured polymers (e.g. polycondensates, polyadducts and other fluoropolymers previously reviewed [400, 401]). As mentioned above, a... 

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-... 

Ion-permeable membranes are also made by swelling existing films with styrene and DVB, which can then be post-treated to add functional groups, or by grafting of ion-exchange functional groups directly onto the polymer matrix of existing films. For example, free radicals formed by radiation of polyethylene or fluoropolymer films become sites for addition of vinyl sulfonic acid, acrylic acid or vinyl amines [30]. 

Certain functional groups are inherently stable or unstable. For example, chloropolymers and fluoropolymers degrade relatively easily. Dehydrohalogenation removes a chloride or fluorine atom and the adjacent hydogen to form hydrochloric or hydrofluoric acid. The acids catalyze further degradation and attack processing equipment. Thus, chloropolymers, such as PVC, are always compoimded with heat stabilizers, and special coatings or materials are required for equipment in which chloropolymers and fluoropolymers will be processed. 

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.). 

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