Alexander Shaplov - Ring-Opening Metathesis Polymerization (ROMP) in Ionic Liquids: Scope and Limitations

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      Ya.S. Vygodskii, A.S.   Shaplov, E.I. Lozinskaya, O.A. Filippov, E.S. Shubina, R.   Bandari, M.R. Buchmeiser.   Macromolecules, 2006,   v. 39, P. 7821-7830.


      The ring-opening metathesis polymerization (ROMP) of functional   norbornenes, i.e. exo,endo-5-norbornen-2-carbonitrile   (3), methyl   (exo,endo-5-norbornene-2-carboxylate)   (4), norborn-5-ene-2-yl acetate   (5), 2-propyl   exo,endo-5-norbornene-2-carboxylate   (6), norborn-5-ene-2-carboxylic acid   (7), exo,endo-5-norbornene-2-methanol   (8),   exo,endo-5-norbornene-2-ylmethylbromide   (9),   exo,endo-5-norbornene-2-ylmethylamine   (10), exo,   endo-5-norbornene-2-triethoxysilane (11),   dimethyl exo,endo-5-norbornene-2-yl phosphonate   (12),   exo,endo-5-Norbornene-2-ylcarboxyethyl-3-ethylimidazolium   bis(trifluoromethyl-sulfonyl)imide (13),   exo,endo-5-norbornene-2-ylcarboxyethyl-3-ethylimidazolium   tetrafluoroborate (14),   7-oxanorborn-5-ene-2,3-dicarboxylic anhydride   (15), was performed in a variety of pure ionic   liquids (ILs) in the absence of any co-solvent. Both imidazolium,   i.e. [1-butyl-3-methylIM]+X- and   [1-butyl-2,3-dimethylIM]+X-  (IM+=imidazolium,   X-=PF6-,   CF3SO3-,   (CF3SO2)2N-,   CF3COO-, NO3-,   BF4-, Br-), and   phosphonium-based ILs, i.e.   [P+(C6H13)3(C14H29)]X-  (X-=PF6-,   BF4-, Cl-), were used. In this   context, the principal compatibility of an IL with a series of   ruthenium-based catalysts, i.e.  RuCl2Py2(IMesH2)(CHPh)   (1) and   RuCl2(IMesH2)(2-(2-PrO-C6H4)   (2) (Py=pyridine,   IMesH2=1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolin-2-ylidene)   was shown. The influence of temperature, concentration of both   the initiator and the monomer and nature of the IL on ROMP was   investigated. ROMP of norbornene derivatives in ionic solvents   proceeded with high speed and offered access to high molecular   weight polymers (Mw up to 1,500,000 g/mol) in   high yields. Most important, ILs allowed for the synthesis of   polymers from monomers that are hardly polymerizable in organic   solvents, e.g. of 15. The use of   3 in [1-methyl-3-butylIM]+  PF6- as the reaction medium along with   2-(2-propoxy)styrene allowed for the recycling of the ruthenium   catalyst. The interaction of catalyst 2 with   different ILs, which allowed for an explanation of the influence   of the IL’s nature upon the polymerization process, was   investigated by IR- and UV-Vis-spectroscopy. These investigations   will facilitate the choice of the optimum IL in future   investigations.

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