- Email: [email protected]
Conclusions: What future for fluorine and fluorine products?
Conclusions: What future for fluorine and fluorine products?
We have seen that fluorine, with its long history, is present today in various application fields: in chemistry, of course, but also in biology, medicine, agrochemistry, new technologies, energy transformation, etc. Thanks to its specific properties (very high reactivity and electronegativity, high oxidizing power), fluorine has given rise to a remarkable chemistry and applications. Today, there are more than 600,000 compounds containing at least one fluorine atom, and the chemistry of fluorine and fluorinated products has led to advances in a wide variety of applications. –
–
In chemistry and applied sciences ▪ New molecules with highly selective properties (sulfur-based fluoride compounds used as steroids, triflic acid derivatives, sugars, vitamins). ▪ Fluoropolymers derived from Teflon, whose remarkable resistance to corrosion has revolutionized many domains: the packaging of highly reactive products, nonstick culinary containers, cardiovascular surgery materials, ion exchange membranes, tissues which “breathe” after treatment with Gore-Tex. ▪ Superacid media used for the production of high-octane fuels. ▪ Surfactants used for the protection of surfaces (fabrics, carpets, leather) and for firefighting. ▪ Fluorinated materials with specific properties (catalysts, colored pigments, chemical sensors, biomaterials). ▪ Nanocomposites based on fluorinated silanes and silica, metal and fluorinated polymers with ultrahydrophobic properties, selective membranes for gas filtration. ▪ Surface treatments for the protection of our cultural heritage, antigraffiti and antireflective layers, UV absorbers, car protection. In the storage and conversion of energy, fluorine can be considered an irreplaceable element of the nuclear cycle. Fluorinated products are used as components of batteries and solid electrolytes based on ionic conductors, as well as perfluorinated membranes of the nafion type at the heart of PEM fuel cells. ▪ In photonics and micro-electronics, fluorine and fluorinated gases occupy a strategic place in the production chain of silicon components because they allow the elimination of any trace of impurities on the surface of the semiconductor that would be unacceptable for the functioning of our computers. Ceramics, glasses, and fluorinated glass ceramics are used in the composition of laser fibers, optical amplifiers, and waveguides for telecommunications microlasers. We can add color pigments, UV absorbers for protection of wood furniture, phosphors for television, heavy metal bases for fiber
242
Conclusions: What future for fluorine and fluorine products?
lasers, transparent conducting films (TCF), dye-sensitized-perovskite-quantum-dotsensitized solar cells, LEDs, OLEDs, etc. ▪ In agrochemistry, fluorine is present in half of the molecules with herbicidal, fungicidal, or insecticidal properties. – In environmental protection—After the discovery of the involvement of CFCs, HCFCs, and other PFCs in the depletion of the ozone layer (followed by their final ban) spectacular results have been achieved within fewer than 30 years. The result of research by industrial and academic groups has made it possible to propose new formulations and substitutes which have thus greatly slowed down this type of atmospheric degradation. - In biology, medicine, biotechnologies, phytosanitation—The potential of fluorinated compounds is multifaceted, with fluorinated molecules exhibiting anticancer, antiinflammatory, antibiotic, neuroleptic, antidepressant, anesthetic, or antihypertensive properties. Biomimetic materials use the properties of fluoroapatite, one of the main constituents of our skeleton. Fluorinated blood substitutes could be used for emergency transfusions. Perfluorocarbons are used in vitreoretinal surgery during retinal detachment operations. In the early detection of cancers, positron emission tomography (PET) using the 18F fluorine radioisotope, allows the production of high-quality scans of our organs, tissues, or cells. Over the last 20 years, new tools have become available to fight against certain diseases, thanks to the rapid progress in the organic and bio-organic chemistry of fluorine. Increasingly powerful synthesis methodologies, associated with original and varied fluorinated structural units, make it possible to access the design of new drugs or phytosanitary products with increasingly sophisticated structures. Moreover, the understanding of the multiple effects produced by fluorine atoms on the biological behavior of a molecule is in full development. Thanks to the rapid progress in fluorine chemistry over the last 20 years, powerful new synthesis methodologies and original and varied fluorinated structural motifs are available, and as a result, the design of new drugs with increasingly sophisticated structures is facilitated.
It can be argued that the impact of fluorine and fluorinated products on our daily lives is part of the general context of confrontation between scientific advances and societal benefits, that is, between benefits and prejudices for humans and their environment. The presentation of some major discoveries and technological improvements in fluorine and fluoride products that have punctuated the 20th and early 21st centuries can illustrate this point. Among these advances, some had to be called into question because of serious disturbances caused to humans or the environment. For each of these areas, we have endeavored to show that, as soon as it turned out that these products were likely to create major problems, scientists put everything into play to propose the most appropriate solutions. At the beginning of the century, the benefits of fluorinated compounds are evident in many areas, and the future of this element is very encouraging because of the promising contributions of fluorinated molecules and materials in many fields of science and technology. Nevertheless, drawbacks to our environment caused by some of these products should not be underestimated. Perfluorinated compounds such as PFOA which bioaccumulate in the body are classified as endocrine disruptors, as are other species such as persistent organic pollutants (POPs), pesticides (DDT), polychlorinated biphenyls, polychloroterphenyls, bisphenol A, or phthalates. They may be harming the health of wildlife; the potential health effects of PFOA and other PFCs to humans are under investigation in the United States by the C8 Science Panel [C8 for perfluorooctanoic acid] (http://www.c8sciencepanel.org/).
Conclusions: What future for fluorine and fluorine products?
243
In addition, solutions must be proposed to further limit the emission of gases or fluorinated pollutants into our atmosphere and environment. However, certain aspects of the history of fluorinated products evoked in this book encourage us to remain optimistic. It can be considered that if there had not been a rapid worldwide awareness following the scientific discovery of the ozone layer depletion, the problem could have become rapidly insoluble. This has led researchers and companies to surpass themselves in the search for technological breakthroughs to find new molecules with higher safety, less harmfulness, and more efficiency standards. After the global decisions concerning the stratospheric ozone depletion, it can be emphasized that the strong increase in the stratospheric chlorine values observed in the 20th century is anticipated to be reversed in the next decade and possibly return to pre-1980 values around 2050 in the mid-latitudes, and even possibly return to pre-1980 values in polar regions around 2065. Other optimistic examples quoted in this book should be pointed out, such as the discovery of new types of molecules with low GWP, such as hydrofluorophenols (e.g., HFO-1234yf ) for automotive refrigeration, new alternative shorter chain molecules such as perfluorobutane sulfonyl fluoride for replacing phased-out PFOA, the intense efforts for reducing nocive fluoride emissions in aluminum, ceramics, or other polluting industries, and also for limiting the level of fluorine in drinking water in areas where fluorosis occurs (mostly due to geological reasons). This last point is strongly helped by the awareness of the political decision makers and populations who face these risks because of particular geological conditions and bad consumption habits. In all these cases, scientists must be highly encouraged in their quest for finding the best solutions to overcome all these problems and proposing the most adapted solutions.
We have seen that fluorine, with its long history, is present today in various application fields: in chemistry, of course, but also in biology, medicine, agrochemistry, new technologies, energy transformation, etc. Thanks to its specific properties (very high reactivity and electronegativity, high oxidizing power), fluorine has given rise to a remarkable chemistry and applications. Today, there are more than 600,000 compounds containing at least one fluorine atom, and the chemistry of fluorine and fluorinated products has led to advances in a wide variety of applications. –
–
In chemistry and applied sciences ▪ New molecules with highly selective properties (sulfur-based fluoride compounds used as steroids, triflic acid derivatives, sugars, vitamins). ▪ Fluoropolymers derived from Teflon, whose remarkable resistance to corrosion has revolutionized many domains: the packaging of highly reactive products, nonstick culinary containers, cardiovascular surgery materials, ion exchange membranes, tissues which “breathe” after treatment with Gore-Tex. ▪ Superacid media used for the production of high-octane fuels. ▪ Surfactants used for the protection of surfaces (fabrics, carpets, leather) and for firefighting. ▪ Fluorinated materials with specific properties (catalysts, colored pigments, chemical sensors, biomaterials). ▪ Nanocomposites based on fluorinated silanes and silica, metal and fluorinated polymers with ultrahydrophobic properties, selective membranes for gas filtration. ▪ Surface treatments for the protection of our cultural heritage, antigraffiti and antireflective layers, UV absorbers, car protection. In the storage and conversion of energy, fluorine can be considered an irreplaceable element of the nuclear cycle. Fluorinated products are used as components of batteries and solid electrolytes based on ionic conductors, as well as perfluorinated membranes of the nafion type at the heart of PEM fuel cells. ▪ In photonics and micro-electronics, fluorine and fluorinated gases occupy a strategic place in the production chain of silicon components because they allow the elimination of any trace of impurities on the surface of the semiconductor that would be unacceptable for the functioning of our computers. Ceramics, glasses, and fluorinated glass ceramics are used in the composition of laser fibers, optical amplifiers, and waveguides for telecommunications microlasers. We can add color pigments, UV absorbers for protection of wood furniture, phosphors for television, heavy metal bases for fiber
242
Conclusions: What future for fluorine and fluorine products?
lasers, transparent conducting films (TCF), dye-sensitized-perovskite-quantum-dotsensitized solar cells, LEDs, OLEDs, etc. ▪ In agrochemistry, fluorine is present in half of the molecules with herbicidal, fungicidal, or insecticidal properties. – In environmental protection—After the discovery of the involvement of CFCs, HCFCs, and other PFCs in the depletion of the ozone layer (followed by their final ban) spectacular results have been achieved within fewer than 30 years. The result of research by industrial and academic groups has made it possible to propose new formulations and substitutes which have thus greatly slowed down this type of atmospheric degradation. - In biology, medicine, biotechnologies, phytosanitation—The potential of fluorinated compounds is multifaceted, with fluorinated molecules exhibiting anticancer, antiinflammatory, antibiotic, neuroleptic, antidepressant, anesthetic, or antihypertensive properties. Biomimetic materials use the properties of fluoroapatite, one of the main constituents of our skeleton. Fluorinated blood substitutes could be used for emergency transfusions. Perfluorocarbons are used in vitreoretinal surgery during retinal detachment operations. In the early detection of cancers, positron emission tomography (PET) using the 18F fluorine radioisotope, allows the production of high-quality scans of our organs, tissues, or cells. Over the last 20 years, new tools have become available to fight against certain diseases, thanks to the rapid progress in the organic and bio-organic chemistry of fluorine. Increasingly powerful synthesis methodologies, associated with original and varied fluorinated structural units, make it possible to access the design of new drugs or phytosanitary products with increasingly sophisticated structures. Moreover, the understanding of the multiple effects produced by fluorine atoms on the biological behavior of a molecule is in full development. Thanks to the rapid progress in fluorine chemistry over the last 20 years, powerful new synthesis methodologies and original and varied fluorinated structural motifs are available, and as a result, the design of new drugs with increasingly sophisticated structures is facilitated.
It can be argued that the impact of fluorine and fluorinated products on our daily lives is part of the general context of confrontation between scientific advances and societal benefits, that is, between benefits and prejudices for humans and their environment. The presentation of some major discoveries and technological improvements in fluorine and fluoride products that have punctuated the 20th and early 21st centuries can illustrate this point. Among these advances, some had to be called into question because of serious disturbances caused to humans or the environment. For each of these areas, we have endeavored to show that, as soon as it turned out that these products were likely to create major problems, scientists put everything into play to propose the most appropriate solutions. At the beginning of the century, the benefits of fluorinated compounds are evident in many areas, and the future of this element is very encouraging because of the promising contributions of fluorinated molecules and materials in many fields of science and technology. Nevertheless, drawbacks to our environment caused by some of these products should not be underestimated. Perfluorinated compounds such as PFOA which bioaccumulate in the body are classified as endocrine disruptors, as are other species such as persistent organic pollutants (POPs), pesticides (DDT), polychlorinated biphenyls, polychloroterphenyls, bisphenol A, or phthalates. They may be harming the health of wildlife; the potential health effects of PFOA and other PFCs to humans are under investigation in the United States by the C8 Science Panel [C8 for perfluorooctanoic acid] (http://www.c8sciencepanel.org/).
Conclusions: What future for fluorine and fluorine products?
243
In addition, solutions must be proposed to further limit the emission of gases or fluorinated pollutants into our atmosphere and environment. However, certain aspects of the history of fluorinated products evoked in this book encourage us to remain optimistic. It can be considered that if there had not been a rapid worldwide awareness following the scientific discovery of the ozone layer depletion, the problem could have become rapidly insoluble. This has led researchers and companies to surpass themselves in the search for technological breakthroughs to find new molecules with higher safety, less harmfulness, and more efficiency standards. After the global decisions concerning the stratospheric ozone depletion, it can be emphasized that the strong increase in the stratospheric chlorine values observed in the 20th century is anticipated to be reversed in the next decade and possibly return to pre-1980 values around 2050 in the mid-latitudes, and even possibly return to pre-1980 values in polar regions around 2065. Other optimistic examples quoted in this book should be pointed out, such as the discovery of new types of molecules with low GWP, such as hydrofluorophenols (e.g., HFO-1234yf ) for automotive refrigeration, new alternative shorter chain molecules such as perfluorobutane sulfonyl fluoride for replacing phased-out PFOA, the intense efforts for reducing nocive fluoride emissions in aluminum, ceramics, or other polluting industries, and also for limiting the level of fluorine in drinking water in areas where fluorosis occurs (mostly due to geological reasons). This last point is strongly helped by the awareness of the political decision makers and populations who face these risks because of particular geological conditions and bad consumption habits. In all these cases, scientists must be highly encouraged in their quest for finding the best solutions to overcome all these problems and proposing the most adapted solutions.