Stereoregular polymerization of (N-n-octyl-3-carbazoyl)acetylene was successfully performed with a [Rh(NBD)Cl](2) (NBD = norbornadiene) catalyst to afford poly(N-n-octyl-3-carbazoyl)acetylene (PNOCzA) as a new type of possible electron-transporting polymer in fairly high yields when triethylamine, chloroform, or dimethylformamide was used as the polymerization solvent. The resulting polymers were composed of amorphous cis-transoid isomers bearing a yellow color or crystalline cis-transoid isomers having an orange color, called a columnar, as a pi-conjugated molecular assembly at the solid state. The cis-to-trans isomorization of the yellow and orange polymers was induced by compression at 200 kg/cm(2) under vacuum at room temperature for 10 min. The polymers obtained before and after compression were characterized in detail using H-1 NMR, wide-angle X-ray diffraction, laser Raman, electron spin resonance, and diffuse reflective UV-vis (DRUV-vis) methods. The data showed that compression of the orange polymers resulted in not only destruction of the columnar structure but also formation of a trans-transoid isomer. The trans-transoid isomers obtained by compression of the yellow and orange polymers showed to have fairly long trans conjugated sequences in which pi radicals obtained by the rotational scission of the cis C=C bonds can be stabilized as less mobile unpaired electrons. The trans conjugation lengths, n, in the (C=C)(n) created by the compression of the yellow polymer were estimated as ca. 33 and ca. 36 using the DRUV-vis and Raman methods, respectively. The orange polymers bearing the columnar structure were found to show an extremely wide range absorption in the range from 210 nm to a near-infrared region, similar to850 nm, compared with that of the yellow polymer, although the compression induced such a cis-trans isomerization. Therefore, the columnar as the molecular assembly is newly proposed as an important color element in order to control the color of the such conjugated polymer at the solid phase. In the solution H-1 NMR spectrum of the orange polymer observed after the compression, the first methylene proton peak in the n-octyl group attached to the nitrogen of the carbazoyl ring was found to be almost smeared out. This phenomenon was explained by magnetic dipole-dipole interaction between the methylene proton and the unpaired electron which migrated from the main chain to the carbazoyl nitrogen moiety through the delocalization of the unpaired electrons which were generated by the rotational scission of the cis C=C double bonds in the main chain when compressed.