Synthesis and ionic transport of sulfonated ring-opened polynorbornene based copolymers

The N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide (1a) and N-phenyl-exo-endo-norbornene- 5,6-dicarboximide (1b)monomers were synthesized and copolymerized via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine)benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine[1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] rutheniumdichloride (II). Experiments, at distinct monomer molar ratios, were carried out using catalyst I in order to determine the copolymerization reactivity constants by applying theMayo-Lewis and Fineman- Ross methods. Moreover, both catalysts were used to produce random and block high molecular weight copolymers of 1a with 1b and 1a with norbornene (NB) which were further hydrogenated using a Wilkinson’s catalyst. Then, the saturated copolymers underwent a nucleophilic aromatic substitution by reacting with sodium 4-hydroxybenzenesulfonate dihydrate to generate new polynorbornene ionomers bearing fluorinated pendant benzenesulfonate groups. A thorough study on the electrochemical characteristics involving electromotive forces of concentration cells and proton conductivity of cation-exchange membranes based on a block copolymer of norbornene dicarboximides containing structural units with phenyl and fluorinated pendant benzenesulfonate moieties is reported. The study of electromotive forces (emf) of concentration cells with the sulfonated membrane of copolymer 8 separating electrolyte solutions of different concentration indicate that the membranes exhibit high permselectivity to protons and sodium ions at moderately low concentrations. In principle, these results suggest that the membranes can be considered candidates for ionic separation applicationsFinancial support from National Council for Science and Technology of Mexico (CONACYT) (PhD Scholarship to A.A.S.) is gratefully acknowledged. J. Vargas acknowledges CONACYT for a Posdoctoral Fellowship. We thank CONACYT-SEMARNAT and ICyTDF for generous support with contracts 23432 and 4312. We are grateful to Alejandrina Acosta, Salvador López Morales, Miguel Ángel Canseco and Carlos Flores Morales for their assistance in NMR, GPC, thermal properties and AFM, respectively. This work was also supported by the CICYT through the project MAT2008- 06725-C03-01.Peer reviewe