Synthesis of soluble halogenated polyphenylenes. Mechanism for the coupling of halogenated lithiobenzenes

Abstract

A method for the synthesis of soluble polyphenylenes that involves the polymerization of l-halo-4-lithiobenzenes, l-halo-3-lithiobenzenes, and 1,3-and 1,4-dilithiobenzenes in ethereal solvents is described. The lithiobenzenes are prepared from the corresponding dihalogenated benzenes using tertbutyllithium . By varying the monomers and conditions used, a variety of soluble halogenated polyphenylenes can be obtained with weight average molecular weights (Afw) as high as 6000 with polydispersities (Mw/M") equal to ~2.8. The prequenched polymers can exist as multilithiated polymers if 2.0 equiv of tert-butyllithium is used to form the aryllithium intermediates. The polymers are usually amorphous and contain significant amounts of phenylated polyphenylene units capped with halogens. The polymers are soluble in organic solvents such as THF, chloroform, and methylene chloride. Several of the polymers exhibited low melting and glass transition temperatures. The brominated polymers are easily dehalogenated upon treatment with tert-butyllithium in THF at -78 °C followed by quenching with water. The molecular weights of several of the brominated polymers increased upon debromination with tert-butyllithium. When the polymerizations were carried out in the presence of 1,3-diphenylisobenzofuran, o-benzyne intermediates were trapped as their Diels-Alder adducts. LiH appears to be present in significant amounts upon completion of the polymerization.

Synthesis of Polystyrene and Poly(methyl methacrylate) Each with a Phenyl Seleno Group at Terminal Chain End by Radical Polymerization in the Presence of Benzyl Phenyl Selenide as a Photoiniferter

“…Solvents were purified by distillation after appropriate drying. p-Trimethylsilylbromobenzene was prepared from the reaction of p-lithiobromobenzene and chlorotrimethylsilane according to the literature 29 and was purified by distillation. Other reagents were obtained commercially and used without further purification.…”

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

“…Aromatic boronic acids are typically synthesized by lithium–halogen exchange, using alkyllithium reagents with an aromatic halide, or by reaction with magnesium metal to generate an aromatic Grignard reagent; this aryllithium or Grignard reagent is then added to a trialkylborate to generate the aromatic dialkoxyboronate 13–17. The boronic ester is then hydrolyzed with acid or water to generate the boronic acid.…”

“…Furthermore, it may be possible for carbon‐based char or boron carbide–type char to form under the glass layer. Boronic acids are known to release water on thermolysis, thereby leading to boroxine or boronic acid anhydride formation 13–17. These materials, if they contain more than one boronic acid functionality, may form a network polymer system.…”

Radikalische/anionische SRN1‐Typ‐Polymerisation zur Herstellung von Oligoarenen

“…Der Mechanismus dieses neuen Polymerisationsprozesses ist in Schema 1 am Beispiel der Herstellung von Poly(mphenylen) dargestellt. [ [11][12][13][14][15][16]. [12,13] Diese Homokupplung, die wahrscheinlich über ein Biarylradikalanion als Intermediat abläuft, nutzten wir als Initiierungsschritt.…”

“…Ein Mechanismus, bei dem die Polymerisation über Arine als Intermediate [15] in einem anionischen Prozess abläuft, kann daher ausgeschlossen werden. Ein Mechanismus, bei dem die Polymerisation über Arine als Intermediate [15] in einem anionischen Prozess abläuft, kann daher ausgeschlossen werden.…”