New poly(pyrimido[5,4-d]pyrimidine-2,6-diyl) (PPympym) with bulky dialkylamino substituents (-NR2, R = hexyl, decyl) was prepared by organometallic dehalogenative polycondensation using a zerovalent Ni complex. The obtained PPympym was soluble in common organic solvents such as CHCl3 and THF, and GPC analysis (in CHCl3; vs. polystyrene standards) indicated that new Ppympyms had high number-average molecular weights M-n of 19,100-34,000; they also gave a high [eta] value of about 2.1 dl g(-1). PPympym showed strong photoluminescence both in CHCl3 and in film, and greenish-blue electroluminescence from PPympym-based double-layer light-emitting devices (ITO/PEDOTh/PPympym/Ca-Al; PEDOTh, poly(ethylenedioxythiophene)) was observed.