Effect of Fluorinated Substituents on Solubility and Dielectric Properties of the Liquid Crystalline Poly(ester imides)

With the rapid advancement of 5G communication technology, much attention has been paid on high-performance polymers with a low dielectric constant (Dk), a low dielectric loss (Df) and good processability. In order to further research and improve dielectric properties of the liquid crystalline poly(ester imide)s (LCPEIs), four imide dicarboxylic acids (IAs) with fluorinated groups are designed and synthesized. They are then copolymerized with 1,3-phthalic acid (IPA), p-hydroxybenzoic acid (HBA), and bisphenol monomers via solution polycondensation to obtain fluorinated PEIs, whose fluorine content, position of the fluorinated group, and LC behavior are tunable by using different IAs and bisphenol monomers. These PEIs with the highest Tg of 238 °C are soluble in general organic solvents, such as m-cresol, N-methyl-2-pyrrolidone (NMP), chloroform, and so on. PEI-6F25AF exhibits the lowest Dk of 2.60, while LCPEI-6FD shows the lowest Df of 0.0053 at 10 GHz. It is found that high fluorine content and large pendent group can reduce the Dk, while the fluorinated group grafted close to the nitrogen atom and the LC rigid rod-like conformation lead to low Df. We devoutly expect that this research offers some reference for structure design of LCPEIs with both low Dk and Df at high frequency

Uniformly-Dispersed Black Phosphorene as Flame-Retardant Epoxy Composites via Iterative Dispersion Strategy

Black phosphorus (BP) nanosheets are widely used in flame retardant polymers, but the challenge of poor dispersion in polymers increases their additions and raises the cost of BP-based flame-retardant materials. Here, we propose an iterative dispersion strategy that gradually approaches a homogeneous dispersion state by separating aggregates and dispersions in the BP partial dispersion with multiple cycles. An iron(III) trifluoromethanesulfonate functionalized BP (BFF) is utilized for the flame retardant and reinforcing modification of the epoxy matrix to verify the reliability of this strategy, noting that the F element in BFF can achieve dynamic hydrogen bonds with the epoxy-amine system during the curing process, further promoting dispersion. Therefore, epoxy thermosets with only 0.2 wt % BFF loading achieve UL-94 V-0 level with a limiting oxygen index (LOI) of 29.2% through the synergistic effect of iterative dispersion and dynamic hydrogen bond. The formation of hydrogen bonds between BFF and the epoxy matrix also contributes to a significant increase in the mechanical properties. This work provides a reasonable and facile concept to achieve sufficient dispersion of inorganic nanosheets in polymer or organic matrices and also promotes the process of industrial large-scale manufacturing of BP-based fire-retardant materials

Uniformly-Dispersed Black Phosphorene as Flame-Retardant Epoxy Composites via Iterative Dispersion Strategy

Black phosphorus (BP) nanosheets are widely used in flame retardant polymers, but the challenge of poor dispersion in polymers increases their additions and raises the cost of BP-based flame-retardant materials. Here, we propose an iterative dispersion strategy that gradually approaches a homogeneous dispersion state by separating aggregates and dispersions in the BP partial dispersion with multiple cycles. An iron(III) trifluoromethanesulfonate functionalized BP (BFF) is utilized for the flame retardant and reinforcing modification of the epoxy matrix to verify the reliability of this strategy, noting that the F element in BFF can achieve dynamic hydrogen bonds with the epoxy-amine system during the curing process, further promoting dispersion. Therefore, epoxy thermosets with only 0.2 wt % BFF loading achieve UL-94 V-0 level with a limiting oxygen index (LOI) of 29.2% through the synergistic effect of iterative dispersion and dynamic hydrogen bond. The formation of hydrogen bonds between BFF and the epoxy matrix also contributes to a significant increase in the mechanical properties. This work provides a reasonable and facile concept to achieve sufficient dispersion of inorganic nanosheets in polymer or organic matrices and also promotes the process of industrial large-scale manufacturing of BP-based fire-retardant materials

{Ta₁₂}/{Ta₁₆} Cluster-Containing Polytantalotungstates with Remarkable Photocatalytic H₂ Evolution Activity

Four novel polytantalotungstates K₅Na₄[P₂W₁₅O₅₉(TaO₂)₃]·17H₂O (<b>1</b>), K₈Na₈H₄[P₈W₆₀Ta₁₂(H₂O)₄(OH)₈O₂₃₆]·42H₂O (<b>2</b>), Cs₃K_3.5H_0.5[SiW₉(TaO₂)₃O₃₇]·9H₂O (<b>3</b>), and Cs_10.5K₄H_5.5[Ta₄O₆(SiW₉Ta₃O₄₀)₄]·30H₂O (<b>4</b>) were synthesized. Compounds <b>1</b> and <b>3</b> are tris-(peroxotantalum)-substituted Dawson- and Keggin-type derivatives, whereas <b>2</b> and <b>4</b> are tetrameric oligomers containing respectively an unprecedented {Ta₁₂} and {Ta₁₆} cluster core. The photocatalytic activities of <b>2</b> and <b>4</b> for H₂ evolution from water were evaluated. The significantly enhanced performance against the control K₆[P₂W₁₈O₆₂] can be attributed to the modulation of the electronic structures of these novel POMs by Ta incorporation. The highest activity observed so far with the use of <b>2</b> can be further rationalized by the presence of distorted heptacoordinate Ta atoms in the form of TaO₇ pentagonal bipyramid

New Synthetic Approach of Fluorine-Containing Graphene Oxide for Improving Dielectric and Mechanical Properties of Polyimide Composites

A new approach to synthesize fluorine-containing graphene oxide (FCGO) was proposed, in which a less toxic reagent was used rather than fluorine gas or anhydrous hydrogen fluoride. The dielectric and mechanical properties of polyimide composites were improved by incorporating a small amount of FCGO. FCGO served as not only nanofiller to lower the dielectric constant of PI films but also inorganic toughening particles to improve the toughness of PI films. The dielectric constant of PI films with 0.6 wt % FCGO was decreased from 3.33 for pure PI to 2.34. In addition, both the tensile strength and Young’s modulus of PI films with 0.6 wt % FCGO were increased to 141 MPa and 4.95 GPa from 118 MPa and 2.81 GPa for pure PI, respectively. In addition, its tensile energy to break was enhanced to 31.6 MJ/m³ from 20.8 MJ/m³

Lewis-Basic Lanthanide Metal-Organic Framework-Derived Versatile Multi-Active-Site Synergistic Catalysts for Oxygen Reduction Reaction

Oxygen reduction reaction underpins the development of the whole fuel-cell field, where there is a strong impetus to develop efficient and stable catalysts that can replace the precious metal Pt/C. Herein, a series of excellent catalysts for ORR derived from Ce/La dual lanthanide metal-organic framework with functional Lewis-basic sites were synthesized for the first time. The synergistic effect of high concentration of oxygen vacancies from La-embedded CeO₂ and Fe-N<i>_x</i> sites as well as porous structure endows the catalyst superior performance to Pt/C, with a half-wave potential (<i>E</i>_1/2) of 0.870 V and a current density (<i>j</i>) of 5.43 mA/cm². Furthermore, the catalysts are also effective for other nonelectrocatalytic reactions. It is expected that this research will contribute to synthesis of an excellent nonplatinum electrocatalyst for fuel-cell applications, and the oxygen vacancies stabilized in carbon matrix offer a method for versatile catalyst design for other reactions

6-Amino-3-methylpyrimidinones as Potent, Selective, and Orally Efficacious SHP2 Inhibitors

Protein tyrosine phosphatase SHP2 is an oncoprotein associated with cancer as well as a potential immune modulator because of its role in the programmed cell death PD-L1/PD-1 pathway. In the preceding manuscript, we described the optimization of a fused, bicyclic screening hit for potency, selectivity, and physicochemical properties in order to further expand the chemical diversity of allosteric SHP2 inhibitors. In this manuscript, we describe the further expansion of our approach, morphing the fused, bicyclic system into a novel monocyclic pyrimidinone scaffold through our understanding of SAR and use of structure-based design. These studies led to the identification of SHP394 (1), an orally efficacious inhibitor of SHP2, with high lipophilic efficiency, improved potency, and enhanced pharmacokinetic properties. We also report other pyrimidinone analogues with favorable pharmacokinetic and potency profiles. Overall, this work improves upon our previously described allosteric inhibitors and exemplifies and extends the range of permissible chemical templates that inhibit SHP2 via the allosteric mechanism

Optimization of Fused Bicyclic Allosteric SHP2 Inhibitors

SHP2 is a nonreceptor protein tyrosine phosphatase within the mitogen-activated protein kinase (MAPK) pathway controlling cell growth, differentiation, and oncogenic transformation. SHP2 also participates in the programed cell death pathway (PD-1/PD-L1) governing immune surveillance. Small-molecule inhibition of SHP2 has been widely investigated, including in our previous reports describing SHP099 (2), which binds to a tunnel-like allosteric binding site. To broaden our approach to allosteric inhibition of SHP2, we conducted additional hit finding, evaluation, and structure-based scaffold morphing. These studies, reported here in the first of two papers, led to the identification of multiple 5,6-fused bicyclic scaffolds that bind to the same allosteric tunnel as 2. We demonstrate the structural diversity permitted by the tunnel pharmacophore and culminated in the identification of pyrazolopyrimidinones (e.g., SHP389, 1) that modulate MAPK signaling in vivo. These studies also served as the basis for further scaffold morphing and optimization, detailed in the following manuscript

Allosteric Inhibition of SHP2: Identification of a Potent, Selective, and Orally Efficacious Phosphatase Inhibitor

SHP2 is a nonreceptor protein tyrosine phosphatase (PTP) encoded by the <i>PTPN11</i> gene involved in cell growth and differentiation via the MAPK signaling pathway. SHP2 also purportedly plays an important role in the programmed cell death pathway (PD-1/PD-L1). Because it is an oncoprotein associated with multiple cancer-related diseases, as well as a potential immunomodulator, controlling SHP2 activity is of significant therapeutic interest. Recently in our laboratories, a small molecule inhibitor of SHP2 was identified as an allosteric modulator that stabilizes the autoinhibited conformation of SHP2. A high throughput screen was performed to identify progressable chemical matter, and X-ray crystallography revealed the location of binding in a previously undisclosed allosteric binding pocket. Structure-based drug design was employed to optimize for SHP2 inhibition, and several new protein–ligand interactions were characterized. These studies culminated in the discovery of 6-(4-amino-4-methylpiperidin-1-yl)-3-(2,3-dichlorophenyl)­pyrazin-2-amine (SHP099, <b>1</b>), a potent, selective, orally bioavailable, and efficacious SHP2 inhibitor