Abstract
A comprehensive 3D-quantitative structure–activity relationship (QSAR) pharmacophore model was constructed using the values of comprehensive biodegradation/photodegradation effects of 17 organophosphorus flame retardants (OPFRs) evaluated by a normalization method to modify OPFRs with high biodegradation/photodegradation, taking tris(chloro-isopropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCIPP)—which occur frequently in the environment, and are the most difficult to degrade as target molecules. OPFR-derivative molecules TCPP–OH shows the highest improvement in biodegradation and photodegradation (55.48% and 46.37%, respectively). On simulating the biodegradation path and photodegradation path, it is found that the energy barrier of TCPP–OH for phosphate bond cleavage is reduced by 15.73% and 52.52% compared to TCPP after modification, respectively. Finally, in order to further significantly improve its biodegradability and photodegradation, the efficiency enhancement in the biodegradation and photodegradation of TCPP–OH are analyzed under the simulated environment by molecular dynamics and polarizable continuum model, respectively. The results of molecular dynamics show that the biodegradation efficiency of the TCPP–OH increased by 75.52% compared to TCPP. The UV spectral transition energy (4.07 eV) of TCPP–OH under the influence of hydrogen peroxide solvation effect is 44.23% lower than the actual transition energy (7.29 eV) of TCPP.
Highlights
The plasticity and heat resistance of plastic products are often enhanced by the addition of plasticizers and flame retardants during synthesis
Molecules randomly selected as the training set to obtain the (TnPP), cresyl diphenyl were phosphate (CDPP), tris(2-chloroethyl) phosphate (TCEP), tris(p-t-butylphenyl) phosphate (TBPP), tripropyl phosphate (TPrP), triisobutyl phosphate (TiBP), TCIPP, butyl diphenyl phosphate pharmacophore model for the comprehensive biodegradation/photodegradation effects by Hypo-Gen (BdPhP), triphenyl phosphate (TPHP), isodecyl diphenyl phosphate (IDPP), trimethyl phosphate and statistical data(TMP)
The test set consisted of five molecules for the verification of the tripentyl phosphate (TPeP), tris(2-ethylhexyl) phosphate (TEHP), 2-ethylhexyl diphenyl phosphate (EHDPP), triethyl phosphate (TEP), tris(chloro-isopropyl) phosphate (TCPP)) molecules were randomly selected as the comprehensive effect pharmacophore model (Table 3)
Summary
The plasticity and heat resistance of plastic products are often enhanced by the addition of plasticizers and flame retardants during synthesis. The gradual elimination of brominated flame retardants (BFRs) led to its replacement by organophosphorus flame retardants (OPFRs), whose usage increased from about 3 × 105 to 1 × 106 t [1]. Based on their usage, OPFRs are divided into two types, namely, additive and reactive. The additive type adds OPFRs to polymer materials through physical mixing rather than chemical bonding and is exposed to the surroundings through volatilization, leaching, abrasion and dissolution [2]. The reactive OPFRs are chemically bonded to the polymer. They are Polymers 2020, 12, 1672; doi:10.3390/polym12081672 www.mdpi.com/journal/polymers
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