Polyisobutylene-supported second-generation Hoveyda-Grubbs catalyst is shown to be an effective nonpolar phase tag for ring-opening metathesis polymerization (ROMP). The catalytic activities of the supported Rucarbene complex in ROMP are comparable to those of their homogeneous counterparts. The separability of these catalysts leads to lower Ru contamination (0.5 ppm levels) in the polymer products in comparison to the nonsupported Hoveyda-Grubbs catalyst (10 PPM). (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012