Exploring the Modes of Action of Phosphorus-Based Flame Retardants in Polymeric Systems.
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ABSTRACT: Phosphorus-based flame retardants were incorporated into different, easily preparable matrices, such as polymeric thermoset resins and paraffin as a proposed model for polyolefins and investigated for their flame retardancy performance. The favored mode of action of each flame retardant was identified in each respective system and at each respective concentration. Thermogravimetric analysis was used in combination with infrared spectroscopy of the evolved gas to determine the pyrolysis behavior, residue formation and the release of phosphorus species. Forced flaming tests in the cone calorimeter provided insight into burning behavior and macroscopic residue effects. The results were put into relation to the phosphorus content to reveal correlations between phosphorus concentration in the gas phase and flame inhibition performance, as well as phosphorus concentration in the residue and condensed phase activity. Total heat evolved (fire load) and peak heat release rate were calculated based on changes in the effective heat of combustion and residue, and then compared with the measured values to address the modes of action of the flame retardants quantitatively. The quantification of flame inhibition, charring, and the protective layer effect measure the non-linear flame retardancy effects as functions of the phosphorus concentration. Overall, this screening approach using easily preparable polymer systems provides great insight into the effect of phosphorus in different flame retarded polymers, with regard to polymer structure, phosphorus concentration, and phosphorus species.
Project description:A significant increase in life-threatening infections caused by Gram-negative "superbugs" is a serious threat to global health. With a dearth of new antibiotics in the developmental pipeline, antibiotics with novel mechanisms of action are urgently required to prevent a return to the preantibiotic era. A key strategy to develop novel anti-infective treatments is to discover new natural scaffolds with distinct mechanisms of action. Laterocidine is a unique cyclic lipodepsipeptide with activity against multiple problematic multidrug-resistant Gram-negative pathogens, including Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacterales. Here, we developed a total chemical synthesis methodology for laterocidine and undertook systematic structure-activity relationship studies with chemical biology and NMR. We discovered important structural features that drive the antimicrobial activity of laterocidine, leading to the discovery of an engineered peptide surpassing the efficacy of the original peptide. This engineered peptide demonstrated complete inhibition of the growth of a polymyxin-resistant strain of Pseudomonas aeruginosa in static time-kill experiments.
Project description:Carbon fibre reinforced flame-retarded bioepoxy composites were prepared from commercially available sorbitol polyglycidyl ether (SPE) cured with cycloaliphatic amine hardener. Samples containing 1, 2, and 3% phosphorus (P) were prepared using additive type flame retardants (FRs) resorcinol bis(diphenyl phosphate) (RDP), ammonium polyphosphate (APP), and their combinations. The fire performance of the composites was investigated by limiting oxygen index (LOI), UL-94 tests, and mass loss calorimetry. The effect of FRs on the glass transition temperature, and storage modulus was evaluated by dynamic mechanical analysis (DMA), while the mechanical performance was investigated by tensile, bending, and interlaminar shear measurements, as well as by Charpy impact test. In formulations containing both FRs, the presence of RDP, acting mainly in gas phase, ensured balanced gas and solid-phase mechanism leading to best overall fire performance. APP advantageously compensated the plasticizing (storage modulus and glass transition temperature decreasing) effect of RDP in combined formulations; furthermore, it led to increased tensile strength and Charpy impact energy.
Project description:Synthesis of a novel phosphorus and triazole-functionalized flame-retardant (FR) monomer (PTFM) using azide-alkyne "click" reaction between triprop-2-ynyl phosphate and 2-azidoethanol that can impart intumescent FR property to polyurethane foams (PUFs) has been reported. Polyurethane triazole foams (PUTFs) were prepared using the as-synthesized PTFM and a hydroxylated castor polyol with a hydroxyl value of ∼310 mg KOH/g for application as reactive FR rigid foams. PTFM and the castor polyol were characterized for structural elucidation using Fourier transform infrared and 1H, 13C, and 31P NMR. PUTFs with a varying loading content of PTFM were subjected to the lab-scale flame test, cone calorimetry test, Underwriters Laboratory 94 Vertical burning test (UL 94V), and limiting oxygen index (LOI) test. A significant increase in the char yields, reduction in heat release rates, V-1 rating, and 27% of LOI were observed for PUTFs compared to PUFs and proportional to the percentage loading of PTFM. The cumulative effect of nitrogen and phosphorus in PUTFs on their intumescent behavior was evident from the thermogravimetric analysis and scanning electron microscopy micrographs, which were further supplemented by X-ray photoelectron spectroscopy studies, indicating expulsion of N2 and overall improvement in compression strength as well. Such environment-friendly reactive FRs can be good replacements to the halogenated ones.
Project description:The usage of flame retardants in flammable polymers has been an effective way to protect both lives and material goods from accidental fires. Phosphorus flame retardants have the potential to be follow-on flame retardants after halogenated variants, because of their low toxicity, high efficiency and compatibility. Recently, the emerging allotrope of phosphorus, two-dimensional black phosphorus, as a flame retardant has been developed. To further understand its performance in flame-retardant efficiency among phosphorus flame retardants, in this work, we built model materials to compare the flame-retardant performances of few-layer black phosphorus, red phosphorus nanoparticles, and triphenyl phosphate as flame-retardant additives in cellulose and polyacrylonitrile. Aside from the superior flame retardancy in polyacrylonitrile, few-layer black phosphorus in cellulose showed the superior flame-retardant efficiency in self-extinguishing, ~1.8 and ~4.4 times that of red phosphorus nanoparticles and triphenyl phosphate with similar lateral size and mass load (2.5~4.8 wt%), respectively. The char layer in cellulose coated with the few-layer black phosphorus after combustion was more continuous and smoother than that with red phosphorus nanoparticles, triphenyl phosphate and blank, and the amount of residues of cellulose coated with the few-layer black phosphorus in thermogravimetric analysis were 10 wt%, 14 wt% and 14 wt% more than that with red phosphorus nanoparticles, triphenyl phosphate and blank, respectively. In addition, although exothermic reactions, the combustion enthalpy changes in the few-layer black phosphorus (-127.1 kJ mol-1) are one third of that of red phosphorus nanoparticles (-381.3 kJ mol-1). Based on a joint thermodynamic, spectroscopic, and microscopic analysis, the superior flame retardancy of the few-layer black phosphorus was attributed to superior combustion reaction suppression from the two-dimensional structure and thermal nature of the few-layer black phosphorus.
Project description:Serotonin (5-HT) is a neuromodulator involved in regulating mood, appetite, memory, learning, pain, and establishment of left-right (LR) asymmetry in embryonic development. To explore the role of 5-HT in physiology, we have created two forms of "caged" 5-HT, BHQ-O-5HT and BHQ-N-5HT. When exposed to 365 or 740 nm light, BHQ-O-5HT releases 5-HT through one- or two-photon excitation, respectively. BHQ-O-5HT mediated changes in neural activity in cultured mouse primary sensory neurons and the trigeminal ganglion and optic tectum of intact zebrafish larvae in the form of high-amplitude spiking in response to light. In Xenopus laevis embryos, light-activated 5-HT increased the occurrence of LR patterning defects. Maximal rates of LR defects were observed when 5-HT was released at stage 5 compared with stage 8. These experiments show the potential for BHQ-caged serotonins in studying 5-HT-regulated physiological processes.
Project description:Intrinsically flame retardant polyamide 6 (FRPA6) was synthesized by melt polycondensation of caprolactam and 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP). Following this, FRPA6 fibres were prepared by melt spinning. The chemical structure, thermal stability, mechanical and combustion properties of FRPA6 were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, vertical burning measurements, limiting oxygen index (LOI) measurements, cone calorimetry and scanning electron microscopy. The thermal stability of FRPA6 decreased to a certain extent, but the amount of residual char was improved. FRPA6 containing 5 wt% DDP could achieve a V-0 rating with an LOI value of 33.7%. The spinnability of FRPA6 fibres was good and the tenacity at break reached 3.0 cN dtex-1 which met the requirements of textiles. The flame retardancy of FRPA6 fibres was definitely improved and the LOI value of FRPA6-5 fabric could reach 28.4%, thereby showing good prospect in applications.
Project description:The current test strategy for carcinogenicity consists initially of in vivo and in vitro genotoxicity tests. Non-genotoxic carcinogens do not directly induce DNA damage and, as such, go undetected under this test strategy. In a previous study we setup a comparison approach to categorize chemicals having similar modes of action, according to similarity in gene expression. In the current study we will investigate whether this comparison approach can be improved by omptimizing the concentration selection procedure and by testing a concentration range per chemical.
Project description:Flame-retardant polyvinyl alcohol (PVA) membranes with high transparency and flexibility were prepared by mixing an aqueous solution of a phosphorus-containing acrylic acid (AOPA) with PVA. The reaction between AOPA and PVA, the transparency, the crystallinity and the flexibility of the membrane were investigated with Fourier transform infrared spectrometry (FTIR), UV-vis light transmittance, X-ray diffraction and tensile tests, respectively. The limited oxygen index (LOI) and vertical flame (UL 94 VTM), microscale combustion calorimetry, thermogravimetric analysis (TGA) and TGA-FTIR were employed to evaluate the flame retardancy as well as to reveal the corresponding mechanisms. Results showed that PVA containing 30 wt% of AOPA can reach the UL 94 VTM V0 rating with an LOI of 27.3% and retain 95% of the original transparency of pure PVA. Adding AOPA reduces crystallinity of PVA, while the flexibility is increased. AOPA depresses the thermal degradation of PVA and promotes char formation during combustion. The proposed decomposition mechanism indicates that AOPA acts mainly in the condensed phase.
Project description:Summary:Chemical-genomic approaches that map interactions between small molecules and genetic perturbations offer a promising strategy for functional annotation of uncharacterized bioactive compounds. We recently developed a new high-throughput platform for mapping chemical-genetic (CG) interactions in yeast that can be scaled to screen large compound collections, and we applied this system to generate CG interaction profiles for more than 13 000 compounds. When integrated with the existing global yeast genetic interaction network, CG interaction profiles can enable mode-of-action prediction for previously uncharacterized compounds as well as discover unexpected secondary effects for known drugs. To facilitate future analysis of these valuable data, we developed a public database and web interface named MOSAIC. The website provides a convenient interface for querying compounds, bioprocesses (Gene Ontology terms) and genes for CG information including direct CG interactions, bioprocesses and gene-level target predictions. MOSAIC also provides access to chemical structure information of screened molecules, chemical-genomic profiles and the ability to search for compounds sharing structural and functional similarity. This resource will be of interest to chemical biologists for discovering new small molecule probes with specific modes-of-action as well as computational biologists interested in analysing CG interaction networks. Availability and implementation:MOSAIC is available at http://mosaic.cs.umn.edu. Contact:hisyo@riken.jp, yoshidam@riken.jp, charlie.boone@utoronto.ca or chadm@umn.edu. Supplementary information:Supplementary data are available at Bioinformatics online.
Project description:This review aims to describe and critically analyze studies published over the past four years on the application of polymeric dental nanomaterials as antimicrobial materials in various fields of dentistry. Nanoparticles are promising antimicrobial additives to restoration materials. According to published data, composites based on silver nanoparticles, zinc(II), titanium(IV), magnesium(II), and copper(II) oxide nanoparticles, chitosan nanoparticles, calcium phosphate or fluoride nanoparticles, and nanodiamonds can be used in dental therapy and endodontics. Composites with nanoparticles of hydroxyapatite and bioactive glass proved to be of low efficiency for application in these fields. The materials applicable in orthodontics include nanodiamonds, silver nanoparticles, titanium(IV) and zinc(II) oxide nanoparticles, bioactive glass, and yttrium(III) fluoride nanoparticles. Composites of silver nanoparticles and zinc(II) oxide nanoparticles are used in periodontics, and nanodiamonds and silver, chitosan, and titanium(IV) oxide nanoparticles are employed in dental implantology and dental prosthetics. Composites based on titanium(IV) oxide can also be utilized in maxillofacial surgery to manufacture prostheses. Composites with copper(II) oxide nanoparticles and halloysite nanotubes are promising materials in the field of denture prosthetics. Composites with calcium(II) fluoride or phosphate nanoparticles can be used in therapeutic dentistry for tooth restoration.