Synthesis and properties of new polyamides and polyimides derived from 2,2′-dimethyl-4,4′-bis(4-aminophenoxy)biphenyl

Abstract

In this work, we synthesised a new diamine containing noncoplanar 2,2′-dimethyl-biphenylene and flexible aryl ether units, 2,2′-dimethyl-4,4′-bis(4-aminophenoxy)biphenyl (DBAPB), by nucleophilic substitution of 2,2′-dimethylbiphenyl-4,4′-diol with p-chloronitrobenzene in the presence of K 2CO 3, followed by catalytic reduction with hydrazine/PdC system. A series of aromatic polyamides having inherent viscosities of 1.03–1.48 dl g −1 were prepared by direct polycondensation with aromatic dicarboxylic acids using triphenyl phosphite and pyridine as condensing agents. Nearly all of the polymers revealed an amorphous nature and were readily soluble in a variety of organic solvents. These polymer films had a tensile strength ranging from 22 to 65 MPa. The glass transition and melting temperature of these polyamides could be determined by d.s.c. and ranged from 226 to 273°C and 392–438°C, respectively. These polyamides remained fairly stable up to a temperature around or below 400°C. Moreover, 10% mass losses were recorded in the range 467–496°C in nitrogen atmosphere. The new polyimides were synthesised from DBAPB and various aromatic tetracarboxylic dianhydrides by the conventional two-step method which involved ring-opening polyaddition to form poly(amic acid)s and subsequently thermal or chemical cyclodehydration to polyimides. The inherent viscosities of poly(amic acid)s and polyimides were in the range 1.32–2.01 and 0.82–1.10 dl g −1, respectively. These polyimide films had a tensile strength range of 83–139 MPa. These polyimides had glass transition temperatures between 239 and 303°C. Thermogravimetric analyses demonstrated that almost all polymers were stable up to 450°C, and the 10% mass loss temperatures were recorded in the range 488–534°C in nitrogen.