Tuning the properties of α,ω-bis(trialkoxysilyl) telechelic copolyolefins from ruthenium-catalyzed chain-transfer ring-opening metathesis polymerization (ROMP)

The synthesis of low viscosity liquid α,ω-bis(trialkoxysilyl) telechelic copolyolefins (DF) via ring-opening metathesis polymerization (ROMP)/cross metathesis (CM) is reported. Copolymerization of a norbornene-based olefin (NB-OLF = norbornene (NB), ethylidene norbornene (ENB), methyl 5-norbornene-2-carboxylate (NBCOOMe), methyl 5-oxanorbornene-2-carboxylate (oxaNBCOOMe), or dicyclopentadiene (DCPD)) with a monocycloolefin (mOLF = cyclooctene (COE), 1,5-cyclooctadiene (COD), or 1,5,9-cyclododecatriene (CDT)) was carried out at 40 °C (except for DCPD at 23 °C) in CH2Cl2 for 24 h, using Grubbs' 2nd generation catalyst (G2) and the bis(trialkoxysilyl)-functionalized symmetric acyclic alkene (RO)3Si(CH2)3NHC(O)OCH2CHCHCH2OC(O)NH(CH2)3Si(OR)3 (R = Me or Et) as the chain-transfer agent (CTA). The catalytic productivity (turnover numbers, TONs, up to 50 000 mol(comonomers) mol(Ru)-1 and 1250 mol(CTA 1) mol(Ru)-1) and selectivity (>85 wt%; only minor amounts of cyclic non-functionalized copolymers (CNFs) formed) toward the formation of the corresponding DFs were quite high, as evidenced by fractionation experiments and detailed 1D and 2D 1H and 13C NMR spectroscopy and SEC analyses. The thermal and rheological properties of the random copolymers, assessed by DSC and viscosimetric analyses, could be tuned according to the nature and the ratio of the comonomers. At 23 °C, P(NBCOOMe-co-COE) and P(oxaNBCOOMe-co-COE) synthesized from a 50:50 ratio of comonomers displayed the lowest viscosity. Such silyl-modified polyolefins (SMPOs) are thus foreseen in possible industrial applications as one-component adhesives.