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Synthesis and properties of novel polyamides containing sulfone-ether linkages and xanthene cardo groups



In order to obtain polyamides with enhanced solubility and processability, as well as good mechanical and thermal properties, several novel polyamides containing sulfone-ether linkages and xanthene cardo groups based on a new diamine monomer, 9,9-bis[4-(4-aminophenoxy)phenyl]xanthene (BAPX), were investigated. The BAPX monomer was synthesized via a two-step process consisting of an aromatic nucleophilic substitution reaction of readily available 4-chloronitrobenzene with 9,9-bis(4-hydroxyphenyl)xanthene in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Four novel aromatic polyamides containing sulfone-ether linkages and xanthene cardo groups with inherent viscosities between 0.98 and 1.22 dL g−1 were prepared by low-temperature polycondensation of BAPX with 4,4′-sulfonyldibenzoyl chloride, 4,4′-[sulfonyl-bis(4-phenyleneoxy)]dibenzoyl chloride, 3,3′-[sulfonyl-bis(4-phenyleneoxy)]dibenzoyl chloride and 4,4′-[sulfonyl-bis(2,6-dimethyl-1,4-phenyleneoxy)]dibenzoyl chloride in N,N-dimethylacetamide (DMAc) solution containing pyridine. All these new polyamides were amorphous and readily soluble in various polar solvents such as DMAc and N-methylpyrrolidone. These polymers showed relatively high glass transition temperatures in the range 238–298 °C, almost no weight loss up to 450 °C in air or nitrogen atmosphere, decomposition temperatures at 10% weight loss ranging from 472 to 523 °C and 465 to 512 °C in nitrogen and air, respectively, and char yields at 800 °C in nitrogen higher than 50 wt%. Transparent, flexible and tough films of these polymers cast from DMAc solution exhibited tensile strengths ranging from 78 to 87 MPa, elongations at break from 9 to 13% and initial moduli from 1.7 to 2.2 GPa. Primary characterization of these novel polyamides shows that they might serve as new candidates for processable high-performance polymeric materials. Copyright © 2010 Society of Chemical Industry