Structure of poly‐1.3‐pentadiene prepared with lithium initiators

Abstract

Abstract The microstructure of poly‐1.3‐pentadiene prepared with lithium metal or lithiumalkyles in hydrocarbon solution has been studied by NMR spectroscopy (60 MHz and 100 MHz) and by IR spectroscopy. It was found that the chemical shifts (CHCl 3 solution) of methyl protons in 1.4 units were δ(ppm) = 0.94 and 0.91, corresponding to cis and trans configurations of the double bonds in the polymer backbone, respectively, and that the chemical shifts of the methyl protons in 1.2 units were δ(ppm) = 1.66 and 1.60 corresponding to cis and trans configurations, respectively. As a result, the method of analysis for microstructure was established. Furthermore, the sequence of units in 1.4 structure of these polymers has been measured by IR studies on the hydrogenated polymers. According to this result, the ratio of the head‐to‐head/head‐to‐tail sequences among 1.4 units in poly‐1.3‐pentadiene was found to be 0.05 to 0.06.