Fluorinated ortho-linked polyamides derived from non-coplanar 1,1′-thiobis(2-naphthol): synthesis and characterization

Abstract

A novel sulfide-bridged bis(ether amine) monomer containing bulky trifluoromethyl and naphthyl substituents, 1,1′-thiobis[2-(4-amino-2-trifluoromethylphenoxy)naphthalene], was synthesized from the halogen displacement of 2-chloro-5-nitrobenzotrifluoride with 1,1′-thiobis(2-naphthol) in the presence of potassium carbonate, followed by the palladium on activated carbon-catalyzed reduction of bis(ether nitro) intermediate, 1,1′-thiobis[2-(4-nitro-2-trifluoromethylphenoxy)naphthalene], with hydrazine hydrate in refluxing ethanol. New series of fluorinated poly(ether amide)s (PEA-1–8) were synthesized from bis(ether amine) with various commercially available aromatic diacids (1–8) via a direct polycondensation method with triphenyl phosphite and pyridine. The resulting polymers had inherent viscosities, ranging from 0.61 to 0.93 dl g–1. All the polymers showed outstanding solubility and could be easily dissolved in amide-type polar aprotic solvents (for example, N-methyl-2-pyrrolidone, dimethyl sulfoxide and N,N-dimethylacetamide (DMAc)), and even dissolved in less polar solvents (for example, pyridine, tetrahydrofuran and chloroform). In addition, these polymers could be cast into transparent, flexible and tough films from DMAc solutions. The glass-transition temperatures were recorded between 209 and 251 °C, and 10% weight loss temperatures were in excess of 470 °C in nitrogen and 450 °C in air atmosphere. Moreover, these PEAs exhibited low refractive indices (n=1.5614–1.5813), birefringence (Δ=0.0055–0.0097) and dielectric constants (ɛ=2.68–2.75).