Preparation and characterization of poly(p-phenylenediamine-co-xylidine)

p-Phenylenediamine (PPDA) homopolymer and its copolymers with 2,3-xylidine (XY) were synthesized by oxidative polymerization using potassium persulfat e as an oxidant in HCl medium at room temperature. The yield, intrinsic vis cosity, and solubility of the polymers were significantly dependent on the monomer ratio. The resulting polymers were characterized by Fourier transfo rm IR spectroscopy, H-1-NMR spectroscopy, wide-angle X-ray diffraction, and thermogravimetry methods. The results showed that the number-average degre e of polymerization of the PPDA homopolymer was 33 and the actual content o f XY units in the copolymer was slightly higher than the feed XY unit conte nt. The polymers were substantially amorphous and showed the strongest diff raction at a Bragg angle of 3 degrees. The polymers exhibited a thermal dec omposition temperature higher than 436 degreesC, the maximum weight-loss ra te was slower than 4%/min, and the char yield was larger than 24 wt % at 60 0 degreesC in nitrogen. The activation energy of thermal decomposition for the polymers increased from 19 to 25 kJ/mol with increasing XY unit content s from 0 to 10 mol %. The polymers showed higher thermostability but lower activation energy of decomposition in nitrogen than in air. (C) 2001 John W iley & Sons, Inc.