Fluorine-containing polymers copolymers

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

The processability of fluorine-containing polymers is improved by replacement of one or more of the fluorine atoms. Replacing one of the eight fluorine atoms with a trifluoromethyl group gives a product called FEP or Viton, actually a copolymer of tetrafluoroethylene and hexafluoropropylene (Equation 6.53). Polytrifluoromonochloroethylene (PCTFE, Kel F) (Equation 6.54), in which one fluorine atom has been replaced by a chlorine atom, has a less regular structure and is thus more easily processed. Poly(vinylidene fluoride) (PVDF, Kynar) (Equation 6.55) is also more easily processable but less resistant to solvents and corrosives. 

Block and graft copolymers were prepared by Akutin, Parlashke-vich, Kogan, Kalinina, and Menes (128) by the use of ultrasonics on solutions of fluorine containing polymers or polysiloxanes on one hand and polymethyl methacrylate, polyvinyl chloride, ethylcellulose on the other. 

Other fluorine-containing polymers, such as polychlorotrifluoroethy-lene, polyvinylidenefluoride, polyvinylfluoride, ethylene-tetrafluoroethylene coplymer, and ethylene-chlorotrifluoroethylene copolymer, will not be covered in this chapter. 

Zhang, Z., Ying, S., and Shi, Z. (1999). Synthesis of fluorine-containing block copolymers via ATRP. 1. Synthesis and characterization of PSt-PVDF-PSt triblock copolymers. Polymer, 40 5) 1341-1345. 

Akutin and co-workers [159] made block and graft copolymer of fluorine-containing polymers or polysiloxanes as one component and poly(methyl methacrylate), poly(vinyl chloride), and ethylcellulose as the second. During the irradiation, samples were withdrawn at regular intervals in order to determine the extent of reaction by the decrease in solution viscosity, rj. In other cases, a recombination of macroradicals into new polymeric species caused an increase in the viscosity. The sign and rate of change of rj was thus different for different systems. 

In this chapter, we focus on the fact that fluorine-containing polymers are in a rare class of polymers that have a high afflnity to supercritical carbon dioxide (O Neill et al, 1998). We describe the polymerization of fluorine-containing block copolymers and their use to selectively localize supercritical carbon dioxide in fluorine-containing domains for introducing nanocellular and nanoporous structures. 

Li, K., Wu, P., and Han, Z. (2002a) Preparation and surface properties of fluorine-containing diblock copolymers. Polymer, 43,4079 086. 

A. Alaaeddine, C. Negrell and B. Ameduri, Recent Advances on New Fluorinated Copolymers Based on Carbonate and 01igo(Ethylene Oxide) by Radical Copolymerization, in Advances in Fluorine-Containing Polymers, ed. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

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