Tetraamine ether

The melting temperatures and thermal stabilities of several polybenzimidazoles are shown in TABLE I. For all aromatic polybenzimidazoies, melting points are over 600 C. Generally, the presence of other structural elements will reduce melting points and thermal stabilities. For example, TABLE I includes polybenzimidazoles condensed from either a tetraamine ether or a diacid ether. Strained polymer structures also reduce polybenzimidazole stability as evidenced by the low melting point of a polymer formed with a biphenyl-2,2 -dicarboxylate. Not surprisingly, the aliphatic, adipic acid forms a much less stable polybenzimidazole than the aromatic examples above it in the table. 

An important mode of oxidation for -phenylenediamines is the formation of ben2oquinonediimines, easily obtained by oxidation with silver oxide in ether solution (17). DHmines undergo 1,4 additions with amines to generate tri- and tetraamines which readily oxidi2e in air to highly conjugated, colored products. An example of this is the formation of Bandrowski s base [20048-27-5] when -phenylenediamine is oxidi2ed with potassium ferricyanide (18). 

The tetratosylate of the linear amine is prepared by the dropwise addition of 477 g (2.5 mole) of p-toluenesulfonyl chloride dissolved in 2.5 L of diethyl ether to a solution of 80 g (2 mole) of sodium hydroxide and 94.2 g (0.5 mole) of the linear tetraamine in 200 mL of water. The mixture is vigorously stirred by a mechanical stirrer during the addition and for an hour after its completion. The resulting sticky paste is chilled in an ice bath and then removed by filtration. It is washed well with diethyl ether and water and thoroughly dried in a vacuum at 50° to obtain a clumpy white powder. After recrystallization from methanol, 300-350 g (70-90%) of the tetratosylate is obtained, mp 126-127°. 

Epoxide adhesives comprise epoxy resin, many of which are prepared from phenols and epichlorohydrin, for example, the diglycidyl ether of bis-phenol A or bis-phenol F usually, these resins are a mixtnre of molecular weights blended to fit the applications. The most-common cnratives for epoxy resins are polyanfines (used in stoichiometric amounts), usually a chain-extended primary aliphatic amine, for example, diethylene triamine or triethylene tetraamine or chain-extended equivalents, which react rapidly with the epoxy resin at room temperature. Aromatic amines react slowly at room temperature but rapidly at higher temperatures. Most epoxide adhesives also contain catalysts, typically, tertiary amines. Dicyanimide is the most-common curative for one-component high-temperature-cured epoxide adhesives. Mercaptans or anhydrides are used as curatives for epoxide adhesives for specialist applications, for example, for high-speed room-temperature cures or for electronic applications. A smaller number of epoxide adhesive are cured by cationic polymerization catalysed by Lewis acids photogenerated at the point of application. Lewis acid photoinitiators include diaryliodonium and triarly sulphonium salts. See Radiation-cured adhesives. 

Polybenzimidazoles are synthesized from aromatic tetraamines (bis-o-diamines) and dicarboxylates (acids, esters or amides). Generalized monomers are shown in FIGURE 1 and polybenzimidazoles from those monomers are shown in FIGURE 2. In either figure, R(l) and R(2) can be aromatic or aliphatic and may contain other groups as ether, ketone, sulfone, etc. The structures shown do not exhaust all possible benzimidazole polymers. 

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