Synthesis and Gas-Transport Properties of Metathesis Polytricyclononenes Bearing Three Me3Si Groups per Monomer Unit

A new metathesis polynorbornene containing three SiMe3 groups per monomer unit directly connected to the norbornene moiety via Si-C bonds is synthesized. The ring-opening metathesis polymerization of sterically hindered 3,3,4-tris(trimethylsilyl) tricyclononene-7 is success fully conducted in yields 80-85% in the presence of first generation Grubbs catalyst. The corresponding polymer is obtained with molecular weight M-w up to 5.4 x 10(5) Da. It is an amorphous glassy (T-g = 200 degrees C) polymer with high thermal stability. Gas permeability and diffusivity coefficients are studied for a range of gases (He, H-2, O-2, N-2, CO2, CH4). This polymer containing three SiMe3 groups per monomer unit turns out to be more permeable (P(O-2) = 125 Barrer) than similar polymers with one or two SiMe3 groups per monomer unit (P(O-2) = 30-50 Barrer). Wide angle X-ray diffraction, positron annihilating lifetime spectroscopy, as well as Brunauer-Emmett-Teller investigations are also performed and discussed.