2- Bromoterephthalic acid

Bromoterephthaloylchloride Pi mixture of 10 g bromoterephthalic acid, 20 g freshly distilled thionyl chloride, and 1 ml of DMF is refluxed under a stream of nitrogen for 3 h. Next, the excess thionyl chloride is removed by vacuum distillation (about 10 torr).The remaining bromoterephthalic dichloride is converted to bromoterephthalic acid dimethyl ester by adding the four-fold amount of anhydrous methanol.The excess of methanol is taken off on a rotary evaporator or by distillation and the pure bromoterephthalic acid dimethyl ester can be isolated by fractional distillation (p < 0.01 torr) over a... 

Random copolyesters based on bromoterephthalic acid, methyl hydroquinone, and hexane diol have been synthesized. Their mesophase properties were studied by differential scanning calorimetry, optical microscopy, realtime X-ray diffraction and melt rheology. At low molecular weight these copolymers exhibit triphasic behavior, where two mesomorphic phases coexist with an isotropic phase. Fractionation based on solubility in THF enables the identification of two components. Simple statistical arguments are employed to model the polymerization reaction and account for the observed phase behavior. 

In regioregularly substituted RR-BH the bromine substituents are located only on the terephthaloyl unit, whereas in RR-BB both the two structural units contain the substituents. If one polymerizes bromoterephthalic acid with hydroquinone or bromo-... 

Therefore, these polyesters, in the strict sense, should be taken to be random sequence copolyesters arising from the possible positional isomerism of the substituents. For a comparison purpose, the random positional polymers were synthesized in solution or in melt by reaction bromoterephthalic acid and hydroquinone or diacetate of bromohydroquinone. 

A number of dicarboxylic acids were employed including, a series of p-phe-nylene dicarboxyhc acids such as dimethylterephthalic, dimethylterphthalic acid, bromoterephthalic acid, nitroterephthahc acid, terephthalic acid, and dichloroter-ephthalic acid. The best yield of about 50% was achieved from terephthalic acid, consistent with steric concerns being important. A number of aliphatic diacids were employed including ferrocene-1,1 -dicarboxylic acid, fumaric acid, maleic acid, and oxalic acid. 

The following chemicals were utilized as received (from Aldrich unless otherwise noted) phenylphosphoric dichloride (Alfa Inorganics), terephthalic acid, nitroterephthalic acid, methylterephthalic acid, 2,5-dimethylterephthalic acid, tetramethyl-terephthalic, bromoterephthalic acid, 2,5-dichloroterephthalic acid, tetrabromoethylammonium iodide, trlethylamine (Eastman Kodak Co.), tetrabutylphosphonium bromide, l8-Crown-6 and 15-Crown- 5. 

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