Abstract
New polyphenylquinoxalines (PPQs) containing methyl substituents have been synthesized and characterized. The PPQs were prepared by the polycondensation of a newly-developed aromatic tetraketone, 4,4′ -bis(4-benzilyloxy)-3,3′,5,5′ -tetramethylbiphenyl (III) and aromatic tetraamines. Compared with the non-methyl-substituted PPQs derived from 1,4-bis (4-benzilyloxy)benzene (I) and 4,4′ -bis(4-benzilyloxy)biphenyl (II), the obtained polymers exhibited better solubility. They were soluble not only in the common m-cresol and chloroform, but in polar aprotic solvent N-methyl-2-pyrrolidinone (NMP). The polymers showed glass transition temperatures of 325°C for PPQ-IIIa (from III and 3,3′,4,4′ -tetraaminobiphenyl) and 287°C for PPQ-IIIb (from III and 3,3′,4,4′ -tetraaminodiphenyl ether), which were much higher than their analogues. The PPQs exhibited good thermal stability up to 470°C in nitrogen and good optical transparency at 450 nm with a thickness of around 10 μ m. The refractive indices and birefringences of the PPQs were in the range of 1.6998–1.7739 and 0.0002–0.0007, respectively.
Acknowledgments
The authors greatly appreciate the financial supports from the National Nature Science Foundation of China (NSFC) (No. 50873104).