Periodic Reporting for period 1 - REMES (Chiral Flame Retardant Materials: Design, Synthesis and Study of Chirality-Flame Retardancy Relationship between the (R)-Enantiomer and (S)-Enantiomer)
Reporting period: 2019-04-01 to 2021-03-31
Synthetic polymers are widely used in household appliances, cables, wires, electric devices, transportation, construction materials, etc. However, in air condition most polymers are flammable and easy to burn under a relatively high temperature or in the presence of open fire. In many cases, improving flame retardancy of polymers is very important to reduce potential fire risks. Flame retardant materials are extremely important additives in a wide variety of polymeric materials. In decades, versatile phosphorus-containing compounds have been widely used as flame retardants for polymers due to their high efficiency and low toxicity. Moreover,organophosphorus flame retardants have the effect of plasticizing, which can improve flexibility and mechanical strength of polymer materials in the forming process. Thus, to develop late-model organophosphorus flame retardant still is the hot research in current polymer science.
Chirality is one of the basic attributes of nature. In the field of material science, using optically pure chiral compounds to study the distinctive properties and functions that compared with the corresponding racemic compounds is still in the embryonic stage but develop rapidly. However, to date, systematically utilize optically pure chiral compounds as flame retardant materials and explore the chirality-flame retardancy relationship between the (R)-enantiomer and (S)-enantiomer of chiral flame retardants have not been reported.
The main objective of this innovative work is to use optically pure chiral compounds as flame retardants to develop new generation flame retardant polymer composites. In this project, we designed and synthesized a series of chiral phosphorus-containing compounds as flame retardants for epoxy resin, especially to understand the chirality effect towards flame retardancy between the (R)-enantiomer and (S)-enantiomer of chiral flame retardant. This study will give more insights on developing new generation flame retardants.
Chirality is one of the basic attributes of nature. In the field of material science, using optically pure chiral compounds to study the distinctive properties and functions that compared with the corresponding racemic compounds is still in the embryonic stage but develop rapidly. However, to date, systematically utilize optically pure chiral compounds as flame retardant materials and explore the chirality-flame retardancy relationship between the (R)-enantiomer and (S)-enantiomer of chiral flame retardants have not been reported.
The main objective of this innovative work is to use optically pure chiral compounds as flame retardants to develop new generation flame retardant polymer composites. In this project, we designed and synthesized a series of chiral phosphorus-containing compounds as flame retardants for epoxy resin, especially to understand the chirality effect towards flame retardancy between the (R)-enantiomer and (S)-enantiomer of chiral flame retardant. This study will give more insights on developing new generation flame retardants.
Three pairs of (R)-enantiomers and (S)-enantiomers of BINOL phosphonates [(S)-Ph, (R)-Ph, (S)-Me, (R)-Me, (S)-Et and (R)-Et] were designed and synthesized as the study objectives. The yields and enantiomeric excess (ee) values of these BINOL phosphonates were excellent. Their chemical structures and opitical purities were well characterized by 1H NMR, 13C NMR, 31P NMR, HPLC and circular dichroism (CD) spectra.
Epoxy (EP) resin was chosen as the polymer matrix to evaluate the fire retardancy of our new developed optically pure BINOL phosphonates. Totally 14 phosphonate/EP composites were prepared to study their related fire behaviors, thermal behaviours and mechanical properties. Among of the 14 phosphonate/EP composites: 2 samples passed UL94 vertical burning test rating at V-0 level; 12 samples achieved LOI value>30; 5 examples reached the goal of reduction of heat release rate >40%. Most of preliminary results show that the (S)-enantiomers were superior to (R)-enantiomer on flame retardancy.
Epoxy (EP) resin was chosen as the polymer matrix to evaluate the fire retardancy of our new developed optically pure BINOL phosphonates. Totally 14 phosphonate/EP composites were prepared to study their related fire behaviors, thermal behaviours and mechanical properties. Among of the 14 phosphonate/EP composites: 2 samples passed UL94 vertical burning test rating at V-0 level; 12 samples achieved LOI value>30; 5 examples reached the goal of reduction of heat release rate >40%. Most of preliminary results show that the (S)-enantiomers were superior to (R)-enantiomer on flame retardancy.
The fire safety of materials is extremely important to the whole society. So far, very seldom study focuses on the chiral flame retardant materials, especially almost no systematic study on exploring the different flame retardancy between (R)-enantiomer and (S)-enantiomer of chiral flame retardant materials. In this work, optically pure chiral compounds are employed to develop flame retardant polymer composites for the first time. The eco-friendly, economical, easily prepared chiral BINOL phosphonates were demonstrated as excellent chiral flame retardants for epoxy resin. More significantly, chirality-flame retardancy relationship between the (R)-enantiomer and (S)-enantiomer of chiral BINOL phosphates were systematically investigated. The preliminary result of this project facilitates development of a patent, which promise to develope new generation flame retardants in the future.