Synthesis and gas separation properties of metathesis polynorbornenes with different positions of one or two SiMe3 groups in a monomer unit

The metathesis polymerization of 5,5-bis(trimethylsilyl)norbornene, 2,3-bis(trimethylsilyl)norbornadiene, and exo,endo-3,4-bis(trimethylsilyl)tricyclo4.2.1.0^2,5]non-7-ene with the catalysts WCl₆/1,1,3,3-tetramethyl-1,3-disilacyclobutane, RuCl₃/EtOH, and the Grubbs Ru-carbene complex Cl₂(PCy₃)₂Ru=CHPh has been studied. New polymers with yields of up to 98% and M _w = (2?39) × 10⁵ are prepared. New metathesis copolymers of 5-trimethylsilylnorbonene with 5-(hydroxymethyl)norbornene and 5-(trimethylsiloxymethyl)norbornene are synthesized in the presence of the Cl₂(PCy₃)₂Ru=CHPh catalyst with yields of 78 and 98%. The gas-permeability study of the above series of the metathesis polymers containing one or two Me₃Si substituents in each monomer unit shows that the introduction of the second SiMe₃ group markedly improves their transport characteristics. A change in the character of the backbone (polynorbornadiene, polytricyclononene) has a small effect on the permeability of the polymers. The metathesis polynorbornene with two vicinal SiMe₃ groups exhibits higher gas-permeability coefficients than its isomer with germinal substituents. The homopolymer of 5-trimethylsilylnorbornene is characterized by better transport parameters than its copolymers with -OSiMe₃ and -OH substituents.