A self-polymerizable AB-type monomer for Diels-Alder (D-A) polymn. was prepd., and its polymn. was carried out in the melt phase and at high pressure in soln. The former method generated only low-mol.-wt. polymer, but the latter one offered an efficient polymn. with increased mol. wt., due to the effect of high pressure on reactions with a neg. activation vol. A pyridinium p-toluenesulfonate-catalyzed dehydration reaction of the D-A polymer led to a novel arom. ladder polymer, poly(iptycene), which is sol. in common org. solvents and stable up to 350 °C. The NMR and UV-vis spectra of these polymers match the spectra of their corresponding model compds., the synthesis of which is also reported. [on SciFinder(R)]