Synthesis,polymerization and conducting properties of an ionic liquid-type anionic monomer Jonathan Juger,Franck Meyer,Frédéric Vidal * , Claude Chevrot, Dominique Teyssié Laboratoire de Physicochimie des Polymères et des Interfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, F-95031 Cergy-Pontoise Cedex, France a r t i c l e i n f o Article history: Received 25 September 2008 Accepted 21 October 2008 Available online 25 October 2008 a b s t r a c t The synthesis of a new ionic liquid-type monomer has been performed by association of a methacrylate polymerizable group, a polar tri(ethylene oxide) (TEO) spacer, a trifluoromethane sulfonic (TFSI ) anion and a free imidazolium (EMIm + ) cation.The ionic liquid monomer (ILM) has demonstrated a good ther- mal stability and a high ionic conductivity around 2.1 10 3 S cm 1 at 20 °C.The corresponding homo- polymer has shown an ionic conductivity closely related to the monomer (6.5 10 4 S cm 1 at 20 °C), which confirms the ILM as a valuable monomer for the formation of polymeric ionic liquid (PIL) materials. Ó 2008 Elsevier Ltd. All rights reserved. During the last decade,the field of ionic liquids (ILs) has at- tracted much attention due to their beneficial properties and their low impact on environment. Many investigations have been dedi- cated to their use as new media for synthetic chemistry supported by their peculiar physical properties such as chemicalstability, non-volatility and non-flammability. 1 Moreover, their intrinsic behaviour has also been highlighted in materials’ sciences through structural modifications. 2 The ionic liquids are also characterized by a high ionic conduc- tivity, which has broaden their field of applications as electrolyte. 3 Thus,their contribution is frequently encountered in the develop- ment of new functional materials,such as solar cells, lithium batteries,conductive polymer supercondensatorsand artificial muscles. 4 The design of new advanced materials with high-ionic conductivity has been explored by the formation ofmonomers incorporating an ionic liquid part. The main feature of these com- pounds lies in the combination of different active functions, namely a polymerizable group, a polar poly(ethylene oxide) (PEO) spacer and a terminal ionic liquid moiety. 5 As concern the IL segments, the elaboration of monomers containing imidazolium rings has attracted much attention since measurement of one of the highest ionic conductive values was observed with 1,3-ethyl- methylimidazolium (EMIm + ) ((bis) trifluoromethane) sulfonimide (TFSI ). 3a–e In general, the rational design of ionic liquid monomers (ILMs) based on imidazolium derivatives is studied according to two pathways: the imidazolium ring belongs to the matrix back- bone and the anionic partner allows the ionic conductivity within the polymeric ionic liquid (PIL) materials. 6 By reversing the roles, a second approach has consisted in the elaboration ofpolymeric compounds with a free non-symmetric imidazolium cation as mobile entity.This strategy was mainly developed by formation of protic ILs, 7 namely a proton transfer from the acid end chain group to the base. 8 However, the conductivity of the resulting mac- romolecules remains at a low level, probably due to the presence of severalhydrogen bond acceptor sites which decrease the cation movement by competitive interactions. Keen to explore a new con- ducting system based on the imidazolium cation mobility, we fig- ure that the incorporation of ionic pairs without available proton (i.e.,monoalkylated imidazolium cation) should enhance dramati- cally the conductivity. Thus, we investigated the design of the purpose-built monomer 1 which is, comprised three parts: a methacrylate end group, a tri(ethylene oxide) (TEO) spacer and a trifluoromethanesulfonimide anion with 1,3-ethylmethylimidazo- lium counterion (Scheme 1). This structure was motivated by the role played by the three blocks, as reported by several authors. 3 First, the double bond end chain should afford the synthesis of PIL materials by free rad- ical polymerization. As concerns the polar TEO spacer, the segment length is directly involved in the ion motion, and should confer a good ionic conductivity to the resulting polymer. Some research works have demonstrated that polymeric materials exhibit a good ionic conductivity with pendant chains composed of three to eight ethylene oxyde units. 8 Finally, it was shown that a non-symmetric imidazolium cation should induce a high-ionic conductivity with respect to a mobile anion. 3 0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2008.10.096 * Corresponding author.Tel.: +33 1 34 25 70 52; fax: +33 1 34 25 70 70. E-mail address: frederic.vidal@u-cergy.fr (F. Vidal). N N + - Polymerizable group Polar spacer: TEO Ionic part O O O NH O NH O N S O O F F F 2 Scheme 1. Structure of the ionic liquid ILM1. Tetrahedron Letters 50 (2009) 128–131 Contents lists available at ScienceDirect Tetrahedron Letters j o u r n a l h om e pa ge : w w w . e l s e v i e r . c o m / l o c a t e / t e t l e t