TY - JOUR
T1 - Cis/trans Gradients in living ring-opening metathesis polymerization
AU - Bishop, John P.
AU - Register, Richard A.
N1 - Funding Information:
The authors gratefully acknowledge the National Science Foundation (Polymers Program, DMR-0505940 and -1003942) for financial support of this work, Dr. Carlos Pacheco of Princeton University for assistance with NMR spectroscopy, and Dr. Andrew Bell of Promerus LLC for providing the MTD monomer.
PY - 2010/8
Y1 - 2010/8
N2 - The chain microstructure (cis/trans ratio) in ring-opening metathesis polymerization (ROMP) of norbornene and methyltetracyclododecene (MTD) using the Schrock-type initiator Mo(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(OCMe3)2 is shown to be a strong function of monomer concentration, providing a convenient means for tuning the average trans content in the resulting polymers. Moreover, since this is a "living" ROMP initiator, chains formed in batch polymerizations show a continuous gradient of trans content down the chain, with the trans content increasing with conversion. This gradient can be quite substantial; for a typical norbornene polymerization, trans content varies from 30% at one end of the chain to nearly 80% at the other end. The results are explained based on a literature kinetic description for the behavior of this initiator, where cis and trans units are added to the chain by syn and anti rotamers of the active site, respectively. A quantitative mathematical description is developed for the chain microstructure, and associated kinetic parameters are measured for norbornene and MTD at room temperature. The model accurately describes both the variation in average trans content with starting monomer concentration, and the gradients in trans content measured via samples taken at different conversions throughout the polymerization. In contrast, ROMP of MTD using the first-generation Grubbs' initiator Ru(CHPh)Cl2(PCy3)2 shows no down-chain gradient in trans content.
AB - The chain microstructure (cis/trans ratio) in ring-opening metathesis polymerization (ROMP) of norbornene and methyltetracyclododecene (MTD) using the Schrock-type initiator Mo(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(OCMe3)2 is shown to be a strong function of monomer concentration, providing a convenient means for tuning the average trans content in the resulting polymers. Moreover, since this is a "living" ROMP initiator, chains formed in batch polymerizations show a continuous gradient of trans content down the chain, with the trans content increasing with conversion. This gradient can be quite substantial; for a typical norbornene polymerization, trans content varies from 30% at one end of the chain to nearly 80% at the other end. The results are explained based on a literature kinetic description for the behavior of this initiator, where cis and trans units are added to the chain by syn and anti rotamers of the active site, respectively. A quantitative mathematical description is developed for the chain microstructure, and associated kinetic parameters are measured for norbornene and MTD at room temperature. The model accurately describes both the variation in average trans content with starting monomer concentration, and the gradients in trans content measured via samples taken at different conversions throughout the polymerization. In contrast, ROMP of MTD using the first-generation Grubbs' initiator Ru(CHPh)Cl2(PCy3)2 shows no down-chain gradient in trans content.
KW - Cis/trans Isomerism
KW - Polymerization kinetics
KW - Ring-opening metathesis polymerization
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U2 - 10.1016/j.polymer.2010.06.061
DO - 10.1016/j.polymer.2010.06.061
M3 - Article
AN - SCOPUS:77955560094
SN - 0032-3861
VL - 51
SP - 4121
EP - 4126
JO - Polymer
JF - Polymer
IS - 18
ER -