Macromolecular Nanotechnology Effect of ionic liquid on dielectric, mechanical and dynamic mechanical properties of multi-walled carbon nanotubes/polychloroprene rubber composites Kalaivani Subramaniam a , Amit Das a,⇑ , Dagmar Steinhauser b , Manfred Klüppel b , Gert Heinrich a,c a Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany b Deutsches Institut für Kautschuktechnologie e.V., Eupener Str. 33, 30519 Hannover, Germany c Technische Universität Dresden, Institut für Werkstoffwissenschaft, Helmholtzstrasse 7, 01069 Dresden, Germany article info Article history: Received 21 March 2011 Received in revised form 21 September 2011 Accepted 26 September 2011 Available online 2 October 2011 Keywords: Carbon nanotubes Polychloroprene rubber Electrical conductivity Ionic liquids abstract This paper focuses on the influence of ionic liquid on carbon nanotube based elastomeric composites. Multi-walled carbon nanotubes (MWCNTs) are modified using an ionic liquid at room temperature, 1-butyl 3-methyl imidazolium bis (trifluoromethylsulphonyl) imide (BMI) and modified MWCNTs exhibit physical (cation–p/p–p) interaction with BMI. The polychloroprene rubber (CR) composites are prepared using unmodified and BMI modified MWCNTs. The presence of BMI not only increases the alternating current (AC) electrical con- ductivity and polarisability of the composites but also improves the state of dispersion of the tubes as observed from dielectric spectroscopy and transmission electron microscopy respectively. In addition to the hydrodynamic reinforcement, the formation of improved fil- ler–filler networks is reflected in the dynamic storage modulus (E 0 ) for modified MWCNTs/ CR composites in amplitude sweep measurement upon increasing the proportion of BMI. Hardness and mechanical properties are also studied for the composites as a function of BMI. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Polymer composites based on nano-sized fillers have become one of the most active research fields in polymer science. And the driving force of this research is the versa- tile shape and size of nano-fillers like one dimensional car- bon nanotubes (CNTs) and two dimensional clay platelets. Among these nano-fillers, an arduous attention has been paid on the low dimensional CNTs due to their superlative mechanical and electrical properties right from its discov- ery by the electron microscopist Iijima in 1991 [1]. Poly- mer nanocomposites based on CNTs have been first reported by Ajayan et al. in 1994 [2] and later on exten- sively continued by other researchers in the world. Owing to the large surface area per unit volume of CNTs and its high aspect ratio, a substantial increment in mechanical properties with lower percolation was expected. On con- trary, the poor dispersion and the rope like entanglements of CNTs caused significant weakening of the composites [3]. Different preparation routes as for example: solution blending, melt blending and in situ polymerization in case of thermoplastics [4]; dry mixing and wet mixing in case of elastomers [5] have been attempted to utilize the extra-or- dinary reinforcement of CNTs; and the resulting properties were reported to be affected by the nature of the matrix 0014-3057/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2011.09.021 Abbreviations: IL, ionic liquid; BMI, 1-butyl 3-methyl imidazolium bis (trifluoromethylsulphonyl) imide (room temperature ionic liquid); CNTs, carbon nanotubes; MWCNTs, multi-walled carbon nanotubes; CR, chloro- prene rubber; DSC, differential scanning calorimetry; DMA, dynamic mechanical analysis. ⇑ Corresponding author. Tel.: +49 351 4658 545; fax: +49 351 4658 362. E-mail address: das@ipfdd.de (A. Das). European Polymer Journal 47 (2011) 2234–2243 Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY