High-solubility aromatic polyesters with fluorene and phthalein groups: Synthesis and property

A series of aromatic polyesters bearing fluorene and phthalein groups were synthesized from commercially available 9,9-bis(4-hydroxyphenyl)fluorene (BPF), phenolphthalein, and terephthaloyl chloride through an interfacial polymerization method. The microstructure, molecular weight, morphology, thermal properties, and thermal decomposition mechanism of these aromatic polyesters were investigated. Their mechanical properties were also evaluated. The results suggested that the copolymer compositions were approximately equal to the feed compositions. Moreover, the increase in the BPF unit content increased the glass transition and weight loss temperatures of the aromatic polyesters, owing to the strong rigidity of the bulky fluorene group. All the polymers were amorphous and exhibited good solubility in common organic solvents. Hence, the synthesized polymers could be easily cast into flexible films. The copolymer film samples exhibited better mechanical properties than those of the homopolymers. The tensile strength, Young's modulus, and elongation at break of the polymers first increased gradually, and then decreased with increasing BPF content. Notably, the copolymers exhibited the best mechanical properties at the BPF content range 30-50%. Owing to their characteristics, these synthesized polymers show great potential for application as high performance membrane materials.