Synthesis and characterization of soluble poly(arylene ether ketone)s with high glass transition temperature based on 3,6-bi(4-fluorobenzoyl)-N-alkylcarbazole

3,6-bi(4-fluorobenzoyl)-N-methylcarbazole and 3,6-bi(4-fluorobenzoyl)-N-ethylcarbazole were synthesized and used to prepare poly(arylene ether ketone)s (PAEKs) with high glass transition temperatures (T-g) and good solubility. High molecular weight amorphous PAEKs were prepared from these two difluoroketones with hydroquinone, phenolphthalein, 9,9-bis(4-hydroxyphenyl)fluorene and 4-(4-hydroxylphenyl)-2,3-phthalazin-1-one, respectively. All these polymers presented high thermal stability with glass transition temperatures being in the range 239-303 degrees C and a 5% thermal weight loss temperature above 460 degrees C. Compared with the T-g of phenolphthalein-based PAEK (PEK-C), fluorene-based PAEK (BFEK) and phthalazinone-based PAEK (DPEK) not containing a carbazole unit, these polymers presented a 30-50 degrees C increase in T-g. Meanwhile, PAEKs prepared from N-ethylcarbazole difluoroketone showed good solubility in ordinary organic solvents, and all polymers exhibited excellent resistance to hydrochloric acid (36.5 wt%) and sodium hydroxide (50 wt%) solutions. In particular, phthalazinone-based PAEK bearing N-ethylcarbazole afforded simultaneously a T-g of 301 degrees C with good solubility. Tensile tests of films showed that these polymers have desirable mechanical properties. The carbazole-based difluoroketones play an important role in preparing soluble PAEKs with high T-g by coordinating the relationship between chain rigidity resulting from the carbazole unit and chain distance from the side alkyl. (c) 2014 Society of Chemical Industry