Exposure of solid poly(1,3-dihydroisothianaphthene) (PDHITN) to thiony
l chloride vapor converted it to doped poly(isothianaphthene) (PITN) w
ith a conductivity of 2 S/cm, one of the highest values reported for P
ITN synthesized by chemical methods. In contrast to dehydrogenation of
PDHITN by sulfuryl chloride there was minimal Cl substitution from th
e thionyl chloride treatment. The PITN formed was blue, not pale yello
w as is obtained with electrochemically oxidized thin films of PITN.