SYNTHESIS AND PROPERTIES OF NEW POLYAMIDES AND POLYIMIDES DERIVED FROM 2,2'-DIMETHYL-4,4'-BIS(4-AMINOPHENOXY)BIPHENYL

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 pres ence of K2CO3, followed by catalytic reduction with hydrazine/Pd-C sys tem. A series of aromatic polyamides having inherent viscosities of 1. 03-1.48 dl g(-1) were prepared by direct polycondensation with aromati c dicarboxylic acids using triphenyl phosphite and pyridine as condens ing agents. Nearly all of the polymers revealed an amorphous nature an d were readily soluble in a variety of organic solvents. These polymer films had a tensile strength ranging from 22 to 65 MPa. The glass tra nsition and melting temperature of these polyamides could be determine d by d.s.c. and ranged from 226 to 273 degrees C and 392-438 degrees C , respectively. These polyamides remained fairly stable up to a temper ature around or below 400 degrees C. Moreover, 10% mass losses were re corded in the range 467-496 degrees C in nitrogen atmosphere. The new polyimides were synthesised from DBAPB and various aromatic tetracarbo xylic dianhydrides by the conventional two-step method which involved ring-opening polyaddition to form poly(amic acid)s and subsequently th ermal or chemical cyclodehydration to polyimides. The inherent viscosi ties of poly(amic acid)s and polyimides were in the range 1.32-2.01 an d 0.82-1.10 dl g(-1), respectively. These polyimide films had a tensil e strength range of 83-139 MPa. These polyimides had glass transition temperatures between 239 and 303 degrees C. Thermogravimetric analyses demonstrated that almost all polymers were stable up to 450 degrees C , and the 10% mass loss temperatures were recorded in the range 488-53 4 degrees C in nitrogen. (C) 1997 Elsevier Science Ltd. All rights res erved.