Regeneration of polycondensation of wholly aromatic poly(azomethine)s with 1,5‐ or 2,6‐substituted naphthalene moiety in main chain

Wholly aromatic poly(azomethine)s with 1,5‐ or 2,6‐substituted naphthalene moiety in the main chains were prepared in aprotic polar solvents or m‐cresol under various reaction conditions. In the polymerization of 1,5‐diaminonaphthalene with terephthalaldehyde, the polymer that synthesized in (HMPA/DMSO) at room temperature for 24 h by adding 5 wt % of calcium chloride and a very small amount of p‐toluenesulfonic acid showed the highest reduced viscosity in all of the polymers from 1,5‐diaminonaphthalene. The reduced viscosity of poly(azomethine)s synthesized from 2,6‐diaminonaphthalene with 2,6‐diformylnaphthalene in m‐cresol and with terephthalaldehyde in HMPA/DMSO were η_red = 0.35 and 0.36, respectively. The thermal analysis showed the poly(azomethine)s had high thermal stability and the glass‐transition temperatures of these polymers are about 250 °C. The X‐ray diffraction showed that they are partially crystalline. They could be polymerized again by second stage polycondensation in polyphosphoric acid. The reduced viscosities of the obtained polymers were about 2–5 times as high as that of the pristine polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1064–1072, 2000