Grafts fluoropolymers

Since an IPMC functions as a pathway for hydrated cations, its properties will be expected to affect the performance of an IPMC actuator. The membrane materials used in IPMCs have so far been limited to a few commercially available perfluorinated ionic polymers, such as Nafion, and the thickness of the IPMC has also been restricted to the available thickness of the commercial membrane [67]. However, IPMC actuators employing new ionic membranes have now been reported [68]. The membranes are prepared from fluoropolymers grafted with polystyrene sulfonic acid (PSSA). IPMCs assembled with these membranes have been shown to exhibit at least several times larger displacements than the Nafion-based IPMC with similar thickness. 

Radiation Grafting of Functional Monomers onto Fluoropolymers... 

Investigations of radiation grafting of functional monomers onto fluoropolymers started in the late 1950s. Since that time several hundred papers and patents have been published, as have several reviews,13-16 and some specific aspects have been considered, but a broad overview has not yet appeared in print. 

Many vinyl monomers were reported to have been grafted onto fluoropolymers, such as (meth)acrylic acid and (meth)acrylates, acrylamide, acrylonitryl, styrene, 4-vinyl pyridine, N-vinyl pyrrolidone, and vinyl acetate. Many fluoropolymers have been used as supports, such as PTFE, copolymers of TFE with HFP, PFAVE, VDF and ethylene, PCTFE, PVDF, polyvinyl fluoride, copolymers ofVDF with HFP, vinyl fluoride and chlorotrifluoroethylene (CTFE). The source of irradiation has been primarily y-rays and electron beams. The grafting can be carried out under either direct irradiation or through the use of preliminary irradiated fluoropolymers. Ordinary radical inhibitors can be added to the reaction mixture to avoid homopolymerization of functional monomers. 

It is a well-known fact that the mechanical properties of fluoropolymers, especially perfluoropolymers, degrade dramatically under irradiation. Nevertheless a considerable improvement of the mechanical properties of the final grafted copolymers was observed in comparison with mechanical properties of the initial irradiated fluoropolymer. Thus it is possible to minimize or completely avoid the degradation of mechanical properties of the final grafted composites in comparison with the initial fluoropolymers by choosing appropriate reaction conditions. 

As was shown, the rate of graft polymerization and the composition of grafted copolymers depend on the monomer concentration, temperature, and the composition of fluorpolymer support. The former also depends on the dose of previous irradiation of the fluoropolymer support. It was assumed that the structure of the composites obtained is close to the core-shell type. 

Grafting of functional monomers onto fluoropolymers produced a wide variety of permselective membranes. Grafting of styrene (with the following sulfonation), (meth)acrylic acids, 4-vinylpyridine, A-vinylpyrrolidone onto PTFE films gave membranes for reverse omosis,32-34 ion-exchange membrane,35-39 membranes for separating water from organic solvents by pervaporation,49-42 as well as other kinds of valuable membranes. 

HorsfaU, J. A. and LoveU, K. V. 2002. Comparison of fuel cell performance of selected fluoropolymer and hydrocarbon based grafted copolymers incorporating acrylic acid and styrene sulfonic acid. Polymers for Advanced Technologies 13 381-390. 

C. Aymes-Chodur, N. Betz, M.C. Porte-Durrieu, Ch. Baquey, A. Le Moel, A FTIR and SEM study of PS radiation grafted fluoropolymers Influence of the nature of the ionizing radiation on the film structure, Nucl. Instrum. Methods Phys. Res. B 151 (1999) 377-385. 

Medical articles such as surgical patches and cardiovascular grafts rely on the long-term stability of fluoropolymers as well as their low surface energy and chemical resistance. 

Also within this category of application is the field of radiation grafting onto pre-existing polymeric substrates. E-beam or gamma sources can be used to initiate grafting onto a range of materials, for example poly(olefin)s, fluoropolymers, and cellulosics. The biocompatibility of poly(olefin)s can be greatly... 

In recent years, we have explored the application of low-temperature atmospheric pressure helium plasma sources to activate polymer surfaces for grafting of various monomers. For laboratory experiments with fluoropolymers such as ETFE as the substrate, the application of the handheld plasma source proved to be very efficient because surface areas of a few square centimeters could be activated in approximately 1 min by sweeping the plasma jet over the surface. Samples were reacted with ambient air to enable the formation of (hydro)peroxides and subsequently subjected to grafting. Successful... 

Figure 2.10 Micro-grafting using atmospheric pressure plasma. (A) Activation of a fluoropolymer foil throi h a silicon stencil mask using cm atmospheric helium plasma jet. (B) After grafting of 4 VP anti reaction with iotio-methane to form a strong polyelectrolyte, distinct differences in surface chemistry are evident from differences in wetting in water vapor. (C) After immersion in water, droplets remain only in the grafted areas.

Parquet P, Padeste C, Solak HH, Gursel SA, Scherer GG, Wokaun A. Extreme UV radiation grafting of glycidyl methacrylate nanostructures onto fluoropolymer foils by RAFT-mediated polymerization. Macromolecules 2008 41(17) 6309-16. 

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