Synthesis of new aromatic polyamides, polyimides, and poly(phenylene oxide) containing a bulky pendent group

Abstract

New aromatic polyamides, polyimides, and poly(phenylene oxide) containing a bulky pendent group were synthesized. All of the synthesized high-temperature polymers showed excellent properties as well as good solubility in a wide range of organic solvents. New soluble aromatic polyamides and polyimides containing a pendent enaminonitrile or enoxynitrile group were synthesized from the new diamine monomers, [(3,5-diaminophenyl)phenylaminomethylidene]propanedinitrile and [(3,5-diaminophenyl)phenyloxymethylidene]propanedinitrile. The synthesized polymers with inherent viscosity ranging from 0.19 to 0.37 dL/g showed good solubility in polar aprotic solvents. The polyamides (PAEANs) and polyimides (PIEANs) containing pendent enaminonitrile group showed good thermal and hydrolytic stability. 5 % weight loss temperatures of PAEANs and PIEANs in nitrogen were above 440 $^\circ C$ and 510 $^\circ C$, respectively. They underwent curing reaction without the emission of volatile by-products around 350 $^\circ C$ to stable materials, which are not soluble in any organic solvents. However, the polyamides (PAEONs) and polyimides (PIEONs) containing pendent enoxynitrile group started to decompose around 300 $^\circ C$ because of the instability of enoxynitrile group. PAEONs underwent curing reaction around 420 $^\circ C$ in spite of initial decomposition, while PIEONs exhibited only thermal degradation process. Thermal analyses of these polymers and the corresponding model compounds confirm that curing reaction proceeds via intermolecular crosslinking as well as intramolecular cyclization. The enoxynitrile group cannot be cured by itself, and reactive amine group is essential for the curing of the enoxynitrile groups. A new poly(phenylene oxide) containing pendent trifluoromethyl group ($CF_{3}-PPO$) was synthesized by nucleophilic aromatic substitution $(S_NAr)$ reaction of 5-fluoro-2-nitrobenzotrifluoride (BC type monomer) with hydroquinone (AA type monomer). Based on t...