Synthesis and Properties of Organosoluble Fluorinated Polyamides Bearing 2-2′-Thio-bis(4-methyl Phenoxy) Groups

A new fluorinated diamine, 2,2′-thio-bis-[4-methyl(2-trifluoromethyl)4-aminophenoxy) phenyl ether] (DA), was successfully synthesized by refluxing dibenzosulfide (DH) and 2-chloro-5-benzotrifluoride 2-chloro-5-nitrobenzotrifluoride in the presence of potassium carbonate, followed by catalytic reduction with zinc/ammonium chloride. Then, a series of organic-soluble polyamides (PAa–PAg) bearing flexible ether and sulfide links, and a electron-withdrawing trifluoromethyl group were synthesized from diamine (DA) with various aromatic diacids (a–g) via direct polycondensation with triphenyl phosphate and pyridine. The polyamides were obtained in quantitative yields and possessed inherent viscosities in the range of 0.35–0.86 dl/g. All the polymers were noncrystalline, showed outstanding solubility and could be easily dissolved in amide-type polar aprotic solvents (e.g., N-methyl-2-pyrrolidinone, N,N-dimethylacetamide and N,N-dimethylformamide) and even dissolved in less polar solvents (e.g., pyridine and tetrahydrofuran). They were in useful levels of thermal stability: 10% weight loss in nitrogen atmosphere was in the range of 375–480°C, depending on the structure of the polymer main chain. The polymers showed glass transition temperatures between 160 and 210°C.