DEVELOPMENT OF SAFE RADICAL INITIATORS FOR POLYMERIZATION (NAR) – NAR

Since the beginning of the era of technology, chemical industry plays pivotal roles spanning from the development of new materials to the development of new drugs. Even, if today, the importance and the attractiveness of the chemistry do not look strong, they are so deeply embedded in our daily life that they cannot be suppressed. Although only noticed when accidents occurred, chemical industry provided jobs to thousand people. Despite the many benefits of chemistry in social and technology fields, it has some detrimental issues concerning environment and technologic risks. More and more drastic regulations are promulgated by the government to improve safety for the population as well as to decrease the detrimental impact of chemical on its environment keeping all technologic and social benefits. This increases dramatically the costs of production leading to question the development of chemical industry in France.
Indeed, the development of the new technology requires the use of new smart materials exhibiting often antagonist properties. The broadest diffusion of new technologies requires selling devices as cheap as possible, and consequently, the latter must be produced using “raw” materials as cheap as possible. This is a high challenge for the chemical industry which must provide smart and cheap materials under the highest requirements for safety and environmental impacts. Hence, chemical industry tackled partly this challenge by using the radical polymerizations RP to produce cheap and smart “raw” materials. Indeed, approximately 50% of all synthetic polymers are currently made via RP. The commercial success of RP can be attributed to the large range of radically polymerizable monomers, their facile copolymerization, the robust reaction conditions employed (typically room temperature to 100 °C, air pressure), and very minimal requirements for purification of monomers and solvents. RP is not affected by water and protic impurities and can be carried out in bulk, solution, aqueous suspension, emulsion, dispersion, etc. The range of monomers is larger for RP than for any other chain polymerization processes because radicals are tolerant to a lot of functionalities, including acidic, hydroxy, and amino groups. In conventional RP, high molecular weight (MW) polymers are formed at the early stages of the polymerization, and neither long reaction times nor high conversions are required, in sharp contrast to step-growth polymerization.1 On the other hand, controlled RPs provide polymers exhibiting various properties and structure in a cheaper than any other techniques of polymerization.
Nevertheless, performing RP requires the use of radical initiators – peroxy and azo compounds – which are prone to decompose thermally. Indeed due to their inherent reactivity, the preparation, storage, handling, and shipping of peroxide derivatives and azo compounds are often challenging and raise severe safety issues. Typically, their extreme exothermic reactivity engenders hazardous risks whether they are stored under unsuitable conditions (e.g. temperature increase).
Therefore, to meet the requirements of the chemical industry, a safe alternative to peroxides derivatives as well as to azo compounds has then to be developed.
Beside the safety concerns with the use of peroxy and azo compounds, environmental and commercial issues arise due to the intrinsic reactivity of the radical generated during the decomposition of theses compounds. Indeed, a part of the generated radicals is prone to react differently – H-atom abstraction and fragmentation reactions – than to add onto monomer and to initiate the RP process. The side-products can be released in the atmosphere with the well-known issues on the air pollution, or released slowly in the final devices generating awful odours to allergies.
Therefore, to meet the requirements of the society: a new generation of initiators combining these safer and “greener” properties needs to be developed