Tuning the molecular weight of ROMP polymers by using Grubbs type catalysts and terminal alkynes

In this study, ruthenium vinyl carbene derivatives were obtained in situ by reacting Grubbs 1st and 2nd generation catalysts with terminal alkynes in toluene at 85 degrees C. These active species were used in ROMP of norbornene derivatives. The effect of alkyne/Ru ( mol/mol) ratio and alkyne substituent on number average molecular weights ( Mn) of ROMP polymers were investigated in detail. ROMP polymers with Mn values between 75 and 680 kDa were synthesized by varying alkyne/Ru ( mol/mol) ratio in the presence of Grubbs type catalysts. The mechanism of the reaction and the role of alkyne in ROMP reactions were investigated in detail by H-1 NMR. (C) 2016 Elsevier B.V. All rights reserved.