Ring-Opening Metathesis Polymerizations in <scp>d</scp>-Limonene:  A Renewable Polymerization Solvent and Chain Transfer Agent for the Synthesis of Alkene Macromonomers

Abstract

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 ( M w ) 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 1 H 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.