We have studied the ring-opening metathesis polymerization of N-cyclohexyl-exo-norbornene-5,6-dicarboximide using the following 4 initiators: Grubbs 1, Grubbs 2, Hoveyda - Grubbs 1 (HG1) and Hoveyda-Grubbs 2 (HG2). Only the Grubbs 1 initiator was able to precisely control the polymer molecular weight. Polymerizations initiated by the HG1, Grubbs 2 and HG2 initiators could not be controlled well. Both the Grubbs 1 and HG1 yielded polymers with a high trans % (85-98%), whereas Grubbs 2 and HG2 yielded polymers with a lower trans % (50-52%). The level of molecular weight control for the four initiators decreased in the order Grubbs 1>HG1>HG2>Grubbs 2. We also demonstrated that, in the case of polymers produced using Grubbs 1, the refractive indices (RIs) of the polymers decreased in a linear and controllable fashion from 1.539 to 1.534 at 633 nm, as the molecular weight was increased from 6700 to 26 400. This change represented a decrease in the RI of 0.005.
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