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

Abstract

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 (Tg) 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 °C and a 5% thermal weight loss temperature above 460 °C. Compared with the Tg 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 °C increase in Tg. 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 Tg of 301 °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 Tg by coordinating the relationship between chain rigidity resulting from the carbazole unit and chain distance from the side alkyl. © 2014 Society of Chemical Industry