Abstract
Selenacyclobutane (trimethylene selenide) readily undergoes photochemical reaction to give polymeric products. Also, the material polymerizes rapidly when the polycrystalline solid film liquifies on a salt substrate in vacuum. Upon polymerization of the sample, infrared and Raman spectra exhibit profound changes which definitely establish ring cleavage. The Raman spectra of the polymer reveal strong CβSe stretching peaks but little or no scattering in the region of SeβSe stretching, strongly suggesting that the polymerization process proceeds in a regular headβtoβtail fashion. An EPR study of the monomer exposed to ultraviolet radiation at β180Β°C supports this fact, since the resulting spectrum is indicative of an intermediate radical species, (CH~2~CH~2~βCH~2~Se)~n~., where n is sufficiently large that the terminal electrons do not interact. No triplet spectra were observed. Molecular oxygen apparently plays an important role in the polymerization kinetics, since it is found that degassed samples of the substance, in contrast to those which have not been degassed, polymerize rapidly even under room illumination. Freezingβpoint depression measurements fix a lower limit to the average molecular weight of the polymer at 2700 (n = 23 monomer units).