High Tg and high organosolubility of novel unsymmetric polyimides

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2009-05, Vol.47 (9), p.2443-2452
• Main Authors: Chern, Yaw-Terng, Tsai, Jeng-Yu, Wang, Jane-Jen
• Format: Article
• Language: English
• Subjects: Applied sciences; dielectric constant; dielectric properties; Exact sciences and technology; glass transition temperature; high performance polymers; Organic polymers; Physicochemistry of polymers; polyimides; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; solubility; thermal properties; unsymmetry
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.23337

A series of new polyimides (PIs) containing di-tert-butyl side groups were synthesized via a polycondensation of 1-(4-aminophenoxy)-4-(4-amino-2-methylphenyl)-2,6-di-tert-butylbenzene (3) with various aromatic tetracarboxylic dianhydrides. The novel unsymmetric PIs exhibited a low dielectric constants (2.78-3.02), low moisture absorption (0.53-1.35%), excellent solubility, and high glass transition temperature (308-450 °C). The PI derived from the new diamine and the very rigid naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) was soluble in N-methyl-2-pyrrolidone, chloroform, m-cresol, and cyclohexanone. The unsymmetric di-tert-butyl pendent groups significantly enhance the rotational barrier of the polymer chains; thus these PIs had high Tgs. The ¹H NMR spectrum of the diamine 3 revealed that the protons of 4-aminophenoxy moiety are not chemical shift equivalent. This is because the steric hindrance of the bulky di-tert-butyl groups prevents the benzene ring of 4-aminophenoxy moiety from rotating freely.