Fast and eco‐friendly synthesis of novel soluble thermally stable poly(amide‐imide)s modified with siloxane linkage with reduced dielectric constant under microwave irradiation in TBAB, TBPB and MeBuImCl via isocyanate method

Abstract

AbstractA new series of poly(amide‐imide)s (PAI) modified with a siloxane linkage was synthesized under microwave radiation in ionic liquids and organic salts via the isocyanate method. The polymerization reactions of a novel siloxanic diacid monomer with 4,4′‐methylene‐bis(4‐phenylisocyanate) MDI were studied in ammonium, phosphonium, and imidazolium‐type organic salts. These poly(amide‐imide‐siloxane)s (PAI‐Si)s were obtained with high yields and good inherent viscosities ranging from 0.30 to 0.55 dL/g. The normally high softening temperatures and poor solubility of PAIs in organic solvents were improved via the incorporation of the flexible siloxane segments into the polymer backbone. The PAI‐Sis showed glass transition temperatures around 100°C and their 10% mass loss was about 300°C. They have a char yield in the range of 30–40% at 800°C. Calculated limiting oxygen index values of the polymers were about 30; therefore, they can be considered as self‐extinguishing. The dielectric constants of these silane‐containing PAIs (2.5) are lower than common siloxane‐free polyimides (∼ 3). Their good thermal stability, enhanced solubility, and low dielectric constants suggest they may function as electrical insulators. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013