Tailored norbornene-based copolymer with systematic variation of norbornadiene as a crosslinker obtained via ROMP with alternative amine Ru catalysts

Copolymers of norbornene (NBE) with norbornadiene (NBD) were obtained via ROMP with [RuCl2(PPh3)2(L)] type complexes as initiators (1 for L = piperidine and 2 for L = 3,5-Me2piperidine). The reactions were performed using a fixed quantity of NBE (5000 equivalents/[Ru]) for different concentrations of NBD (500, 1000, 1500 and 2000 equivalents/[Ru]) in CHCl3, initiated with ethyl diazoacetate at room temperature. The presence of NBD in the NBE chains was characterized by 1H and 13C NMR. Whereas the copolymer microstructure was influenced neither by the NBD quantity nor by the initiator type, the Mn and PDI values were improved when increasing the NBD quantity in the medium. When raising the NBD amount, DMA results indicated increased cross-linking with increasing Tg and E′ storage modulus, as well as the fact that SEM micrographs indicated decreased pore sizes in the porous isolated copolymers.

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► Norbornadiene as a cross-linking agent to change the polynorbornene synthesis.
► Improved Mn and PDI values when increasing the norbornadiene quantity in the medium.
► Copolymers with increased cross-linking with increasing Tg and E′ storage modulus.
► Different pore sizes in the isolated copolymers in agreement with the M2/M1 ratios.
► Monomer reactivity controlled by small changes in the catalyst.