Abstract
During the last decades, the importance of phosphorus-containing halogen-free flame retardants is increasing due to the good environmental sustainability of theses substances. 9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives as prominent members of this group of flame retardants show excellent flame-retardant efficiency in different polymers, where they act in particular in the gas phase. Since the development of DOPO in 1972, a large number of DOPO derivatives have been investigated and synthesized in academia and industry. This review will discuss the advancements of promising DOPO-based compounds regarding their synthesis and flame retardancy in thermosets as well as in thermoplastics.