Comparative Reactivity of Me3Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerization

Abstract

Silyl substituted norbornenes and their derivatives are effective monomers in the synthesis of new prospective polymer materials for gas separation membranes by metathesis and addition polymerization. Comparative activity of norbornenes (NB), norbornadienes (NBD) and tricyclononenes (TCN) with different spatial arrangement of one or two Me3Si substituents in ring-opening metathesis polymerization (ROMP) in the presence of Grubbs initiator Cl2(PCy3)2Ru =CHPh were studied by NMR and GC. It was shown that the rate of the initiation was lower than the propagation for all monomers and the highest activity was inherent to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN turned out to be more active than NB having the same number and position of the substituents. The latter were more active than the corresponding NBD. It was found that syn- and anti-isomers of 3-TCNSi polymerized with close rates in contrast to exo- and endo-substituted 5-NBSi, for which polymerization rates were substantially different. Special behavior of monomers with bulky substituents in the geminal position was observed: 5,5-NBSi2 was inactive in the presence of the 1st generation Grubbs initiator, whereas it was polymerized in the presence of the 2nd generation one. Quantum-chemical calculations were in agreement with experimental data and evidenced the influence of energy, electronic and structural properties of the norbornene-type monomers studied on their activity in ROMP.