Thianthrene-2,7-dicarboxylic acid

Thianthrene-containing polyamides have also been prepared by reacting thianthrene-2,7-dicarboxylic acid chloride with aromatic and aliphatic diamines at low-temperature. The polymerization of thianthrene-2,7-dicarboxylic acid chloride and 1,4-phenylenediamine yielded 81% polyamide with an inherent viscosity of 0.75 dL/g, although no other polymers or characterization results were discussed. 

Thianthrene-2,7-dicarboxylic acid has previously been prepared via direct functionalization of thianthrene, and was investigated as a precursor to dyes and aramids. The latter were prepared from the diacid chloride derivative and were obtained with relatively poor yields and viscosities. The solubility and thermal properties were not reported. 

TTie polyamides prepared here also have low crystallinity as determined by wide angle X-ray (no or weak crystalline peaks seen above strong broad amorphous bases). The thermal stability of thianthrene-based polymers may depend on the basic chemical structure (ie, thianthrene dicarboxylic acid derivatives give aramids which are more stable than those derived from thianthrene diamines) as well as on crystallinity, intermolecular interactions and polymer chain packing. However, the possibility of trace amounts of impurity within Ae thianthrene diamines could have significantly affected the onset of degradation in earlier polymers. 

Thianthrene, 2,3,7,8-tetramethoxy-dication, 3, 968 Thianthrenedicarboxylic acids applications, 3, 993 Thianthrene-2,6-dicarboxylic acids... 

Thianthrene and thioether-containing aromatic dicarboxylic acids were readily synthesized by nucleophilic aromatic substitution. Polyamides obtained from the dacids splayed good thermal stabilities and solubilities enhanced over typical aramids. Films displayed good toughness and flexibility, consistent with high molecular weight and low crystallinity. 

The reaction giving iV,N,N, N-tetramethylthianthrene-2,7- and -2,8-dicarboxamides) generates both isomers in essentially equivalent amounts. The bisamide mixture was hydrolyzed to the thianthrene-2,7- and -2,8-dicarboxylic acids (10 and 11) which could be separated and purified by fractional recrystallization fix>m DMAc/AcOH. The first step of the reaction has been found to give predominantly the 4,4 -thiobis[N, -dimethyl-3-chlorobenzamide] (14), formed first due to the amide group selectively activating the para position for nucleophilic aromatic substitution no evidence was seen for the 3,4 and 3,3 -isomers. 

Thianthrene-2,7- and -2,8-dicarbonyl chlorides were prepared from the dicarboxylic acids with thionyl chloride in approximately 65-80% yield after purification. Poly(phosphoric acid) was used as the polycondensation medium for these polymers. The initial 77.3% P2O5 content kept the viscosity low enough to thoroughly disperse the monomers and was adjusted after dehydrochlorination to give... 

Thianthrenium (thianthrene-2,3-dicarboxylic imide-S-methoxybenzene trifluoromethylsulfonate) is decomposed by UV light to produce acid, as shown in Equation (2.2) ... 

Thianthrene-2,7- and -2,8-dicarboxylic adds plus a synthetic intermediate, 4,4 -thiobis[3-chlorobenzoic acid], were converted to new aromatic polyamides having inherent viscosities of 1.29 to 2.39 dL/g by direct polycondensation with 4,4-oxydianiline and 1,4-phenylenediamine in N-methyl-2-pynolidinone using triphenyl phosphite and pyridine. Thianthrene-based polyamides were more soluble than analogous poly(tluoether amide)s. Polymer films were cast from either DMF or DMAc/LiCl solutions and analyzed by FTIR and NMR. All prepared aramids displayed good thermal stability by DSC and TGA. 

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