Ring-Opening Metathesis Polymerizations in d-Limonene: A Renewable Polymerization Solvent and Chain Transfer Agent for the Synthesis of Alkene Macromonomers
journal contributionposted on 26.12.2006, 00:00 by Robert T. Mathers, Kerry C. McMahon, Krishnan Damodaran, Christopher J. Retarides, Diana J. Kelley
d-Limonene has been utilized as a renewable solvent and chain transfer agent for the ring-opening metathesis polymerization (ROMP) of alkene macromonomers. The polymerization of various strained monomers, such as norbornene and 1,5-cyclooctadiene (COD), and low-strain monomers, such as cyclopentene, trans,trans,trans-1,5,9-cyclododecatriene and cycloheptene, have been initiated with a ruthenium carbene complex. The metathesis reactions with d-limonene resulted in decreased weight-average (Mw) molecular weight values compared to ROMP in toluene and hydrogenated d-limonene. For the ROMP of COD in d-limonene, the amount of chain transfer and chain degradation increased with increasing time (1−20 h) and temperature (23−70 °C). The formation of the trisubstituted alkene during chain transfer, as evidenced by a model compound, was characterized by 1H NMR (δ 5.14 ppm). Optimization of the reaction conditions for the ROMP of COD resulted in the synthesis of alkene macromonomers without the need for postpolymerization reactions.