Synthesis, flame‐retardancy testing, and preliminary mechanism studies of nonhalogenated aromatic boronic acids: A new class of condensed‐phase polymer flame‐retardant additives for acrylonitrile–butadiene–styrene and polycarbonate

Abstract

This study describes the syntheses and thermal properties of aromatic boronic acids and their use as flame retardants. The possible flame-retardancy mechanisms are also discussed. The materials were synthesized from aromatic bromides using one of two procedures. The first procedure involved traditional approaches to boronic acids, using lithium-halogen exchange and quenching with trimethylborate followed by hydrolysis. The second procedure used a nickel catalyst and a dialkoxy borane to generate aromatic dialkoxyboronates that were converted to boronic acids by acid hydrolysis. The thermal properties of these aromatic boronic acids were studied using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). These materials were blended into acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) resins and tested for ignition resistance, using the UL-94 flame test. A 10 wt % loading of 1,4-benzenediboronic acid in polycarbonate gave a UL-94 V-0 result. This same diboronic acid showed flame retardancy and char formation in ABS, but this result was not quantifiable by the UL-94 test. Burn times for the ABS samples often exceeded 5 min, thereby showing unusual resistance to consumption by fire.

Recyclable, Strong, and Highly Malleable Thermosets Based on Boroxine Networks

“…In addition to boronic esters, boroxine is another interesting motif formed by simple dehydration of organic boronic acids . The boroxine motif has been used for several materials applications, including flame retardants, covalent organic frameworks (COFs), and polymers . However, boroxine has not been reported for making malleable polymers.…”

meta-Terphenyl linked donor–π–acceptor dyads: intramolecular charge transfer controlled by electron acceptor group tuning

“…The starting materials, (4-(diphenylamino)phenyl)boronic acid, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile, 2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)benzo[ d ]oxazole, (4-(benzo[ d ]thiazol-2-yl)phenyl)boronic acid, and 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine, were prepared according to the previously reported procedures. 62 All dyads were then synthesized using two-step palladium-catalyzed Suzuki–Miyaura coupling reactions with triphenylamine (TPA) as an electron donor, and cyanide, benzoxazole, benzothiazole, and 2,4-diphenyl-1,3,5-triazine as an electron acceptor. All four compounds were purified by silica gel column chromatography and showed yields in the range of 15 to 75% due to solubility issues.…”

Preparation, structural and thermal studies of boroxine adducts having aryl boronic acids and pyrazoles

“…A large number of boroxine adducts with N-containing compounds have been studied due to wide commercial uses in various field like flame retardant materials, dopants, in SuzukiMiyaura coupling reactions, non-linear optical materials, biosensors, covalent organic frameworks etc. (Bhat et al, 2011;Iovine et al, 2008;Morgan et al, 2000;Mehta and Fujinami, 1997;Yang et al, 2002;Miyaura and Suzuki, 1995;Cote et al, 2005;Türker et al, 2009), but the structural characterization and thermal study of boroxine adducts with pyrazoles are not reported till now. This paper presents the synthesis, structural, and thermal study of four new boroxine adducts.…”