Cyclo‐ and cyclized diene polymers. VIII. Cyclization of polybutadienes and ir spectra of cyclized polybutadiene

Cyclization of cis‐1, 4 and trans‐1, 4‐polybutadiene as of poly (2,3‐dimethyl butadiene‐1,3) was carried out with H2S4 as the cyclization agent. The decrease of the original unsaturation as well as of total unsaturation were measured with IR spectroscopy and the iodine monochloride method, respectively. The kinetics of cyclization were measured and evaluated with an analog computer. Both methods indicate the length of cyclic segments as 25–45 cycles. In the case of poly(2,3‐dimethyl butadiene‐1,3) only monocycles are formed. Some indications of secondary reactions, including isomerization, accompanying the eyclization were given by analyses of IR spectra and chemical analysis.