Abstract
Successful room temperature ring-opening polymerization (ROP) of e-caprolactone and δ-valerolactone has been carried out using SmX2 (X = I, Br, and cyclopentadienyl (Cp)) catalysts. SmI2 in the presence of metallic Sm was found to have enhanced reactivity as room temperature ROP initiator for lactones as compared to pure SmI2. SmBr2 and SmCp2 showed increased reactivity compared with the Sm/SmI2 system due to their higher reductive power. The catalyst concentration and time of polymerization showed a marked effect on number-average molecular weight (Mn). There was a decrease in Mn on increasing reaction time and decreasing catalyst concentration. The initiation mechanism is discussed based on end group analysis of low molecular weight polymers.
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