Preparation and activity of ruthenium catalyst based on β-cyclodextrin for ring-opening metathesis polymerization

Abstract

Inspired by substrates-recognition of enzymes, we prepared supramolecular catalyst (Ru-βCD Cat) for ring-opening metathesis polymerization (ROMP) by modifying second generation Grubbs catalyst® (M204) with β-cyclodextrin (βCD) derivative (VPhe-βCD). The ROMP activity of Ru-βCD Cat was demonstrated using 7-oxanorbornene-2,3-dicarboxylic acid dimethyl ester (ONorCOOMe). The VPhe-βCD cavity recognized the ONorCOOMe monomer and attached to catalytic metal center of Ru-βCD Cat to grow poly(ONorCOOMe) with higher yield and molecular weight (Mn) in aqueous medium. The yield and Mn were higher than those of poly(ONorCOOMe) obtained by second generation Hoveyda-Grubbs catalyst® (M720). 1-Adamantanol hindered ONorCOOMe from occupying the βCD cavity, acting as a competitive guest molecule. The inhibition caused lower polymer yield and Mn. These results showed that molecular recognition of ONorCOOMe by the cavity of Ru-βCD Cat is important to increase the polymer yield and Mn of poly(ONorCOOMe).