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Published March 11, 2009 | Accepted Version + Supplemental Material
Journal Article Open

Pulsed-Addition Ring-Opening Metathesis Polymerization: Catalyst-Economical Syntheses of Homopolymers and Block Copolymers


Poly(tert-butyl ester norbornene imide) homopolymers and poly(tert-butyl ester norbornene imide-b-N-methyloxanorbornene imide) copolymers were prepared by pulsed-addition ring-opening metathesis polymerization (PA-ROMP). PA-ROMP is a unique polymerization method that employs a symmetrical cis-olefin chain transfer agent (CTA) to simultaneously cap a living polymer chain and regenerate the ROMP initiator with high fidelity. Unlike traditional ROMP with chain transfer, the CTA reacts only with the living chain end, resulting in narrowly dispersed products. The regenerated initiator can then initiate polymerization of a subsequent batch of monomer, allowing for multiple polymer chains with controlled molecular weight and low polydispersity to be generated from one metal initiator. Using the fast-initiating ruthenium metathesis catalyst (H_2IMes)(Cl)_2(pyr)_2RuCHPh and cis-4-octene as a CTA, the capabilities of PA-ROMP were investigated with a Symyx robotic system, which allowed for increased control and precision of injection volumes. The results from a detailed study of the time required to carry out the end-capping/initiator-regeneration step were used to design several experiments in which PA-ROMP was performed from one to ten cycles. After determination of the rate of catalyst death, a single, low polydispersity polymer was prepared by adjusting the amount of monomer injected in each cycle, maintaining a constant monomer/catalyst ratio. Additionally, PA-ROMP was used to prepare nearly perfect block copolymers by quickly injecting a second monomer at a specific time interval after the first monomer injection, such that chain transfer had not yet occurred. Polymers were characterized by gel permeation chromatography with multiangle laser light scattering.

Additional Information

© 2009 American Chemical Society. Received November 19, 2008. Publication Date (Web): February 12, 2009. The authors thank Materia for catalyst as well as the NSF (CHE-0410425), the NIH (5RO1GM-31332), and the Gordon and Betty Moore Foundation for funding. Supporting Information Available: Experimental procedures, GPC traces, and derivation of catalyst death rates. This material is available free of charge via the Internet at http://pubs.acs.org.

Attached Files

Accepted Version - nihms95814.pdf

Supplemental Material - Matson2009p1668J_Am_Chem_Soc_supp.pdf


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August 20, 2023
October 19, 2023