Abstract
AbstractThe bulk ring‐opening polymerization (ROP) of ε‐caprolactone (CL), catalyzed by molybdenum trioxide (α‐MoO3), was investigated under nitrogen atmosphere at 150°C. Effect of monomer/initiator ([CL]0/[I]0, I = MoO3) and monomer/initiator/co‐initiator ([CL]0/[I]0/[CoI]0, CoI = ROH and H2O) ratios on monomer conversion and molecular weight were determined. Bulk polymerization of CL was completed within 20 hours at 150°C for [CL]0/[I]0 = 100. Propagation was first order in CL concentration and initiator at this temperature, being the rate constant of propagation kp equal to 2.27 × 10−4 mol−1 l s−1. Polymerization reaction was accelerated by the addition of small amounts of water and n‐octanol. In the presence of water (up to [CL]0/[H2O]0 = 120), polymerization rate increases and was completed within 6 hours at 150°C; for higher amounts of water (150 to 180), lower conversions are observed. However, control of number‐average molecular weight was only efficient for [CL]0/[H2O]0 = 20 and 30. In the presence of n‐octanol, degradation of polyester occurs at early stages of polymerization. Kinetic data for polymerization (obtained by 1H‐NMR) were fitted to 14 different model reaction functions. It was found that a linear model represents better the conversion versus time plots for bulk polymerization, in agreement with the pseudo living nature of polymerization.
Published Version
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