Multiwalled carbon nanotube–polyelectrolyte gels: Preparation and swelling behavior for organic solvents Ali Pourjavadi 1 , Malihe Doulabi 1 Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology, Tehran, Iran abstract article info Article history: Received 28 November 2013 Received in revised form 29 December 2013 Accepted 30 December 2013 Available online 4 February 2014 Keywords: Polyelectrolyte gel Vinylimidazolium Carbon nanotube Organic solvent Swelling behavior In this article, we report the first multiwalled carbon nanotube–polyelectrolyte gel containing vinylimidazolium- typed ionic liquid monomer as an absorbent of less-polar or nonpolar organic solvents. To prepare such MWCNT– polyelectrolyte gel, the modified MWCNTs with polymerizable vinyl groups on their surfaces were prepared and then underwent copolymerizations with dodecyl methacrylate and vinylimidazolium in the presence of AIBN as initiator, yielding a cross-linked polyelectrolyte. In order to estimate the compatibility between the solvents and the polymers, a series of vinylimidazolium-typed ionic liquid monomers ([C n vim][X]) with different alkyl tail length (C 6 ,C 10 and C 12 ) and counter anion (tetrafluoroborate (BF 4 - ), dodecylbenzenesulfonate (DBS - )) were prepared and incorporated into cross-linked polyacrylates. The results showed that the high swelling degree was obtained when the gel matrix had good compatibility with the solvent. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Carbon nanotubes (CNTs) have attracted great interdisciplinary interest since their discovery because of many unique electrical, optical, and mechanical properties that CNTs possess [1,2]. CNTs have the potential of being transformed into new materials that will employ in a wide range of applications, such as sensors, composites, nanoelectronics, biomedical devices, and high-strength fibers [3–10]. Because of their highly porous and hollow structures, large specific surface areas, surface functional groups and hydrophobic surfaces, CNTs have acted as an effec- tive type of adsorbents for the removal of various inorganic and organic pollutants from wastewater [11–13]. Various methods for CNT chemical modification have been applied to introduce functional moieties which contribute to better nanotube dispersion, and eventually to efficient ther- modynamic wetting of nanotubes with polymer matrices [14–16]. Wrap- ping CNTs with polymer chains through covalent and non-covalent functionalization not only improves their compatibility and stability, but also retains the important physical and chemical features of polymers and creates more opportunity for various applications of CNTs. Poly (ionic liquid)s (PILs), a special type of polyelectrolytes with IL species in each of the repeating units, have been very recently intro- duced as a new research focus attracting steadily growing interest in the fields of polymer and material science [17–19]. The properties of PILs commonly prepared via polymerization of monomeric ionic liquids (ILs) are strongly associated with both the polymer and ionic liquid structure, where the structure of the cation and anion (e.g., ion type and substitute groups on the cation) are known to determine the physicochemical properties of ILs [20–22]. Among various types of mo- nomeric ILs, vinylimidazolium salts have received considerable atten- tion because of their favorable properties such as thermal stability, non-flammability, negligible vapor pressure, high charge density and mobility [23,24]. The synergistic effect makes the PIL containing imidazolium salts as a unique class of versatile polyelectrolytes for a va- riety of applications, such as solid ion conductor, CO 2 sorbents, disper- sants, porous materials, and carbon precursors [25–27]. However, application of ILs in polymer science is not limited to traditional poly- merization media. ILs are also investigated as the components of the novel polyelectrolyte gels that exhibit a high degree of swelling in less-polar and nonpolar organic solvents [28–31]. Organic solvents are among the most applied chemicals, and they are considered as the typ- ical organic pollutants in environment contamination. Therefore, the synthesis of highly efficient cleanup materials for recovery of organic solvent spilled in the environment and absorbents for waste oils over water has been gathering ever-growing attention [32–39]. In our previous works [40,41], we demonstrated the first example of polymeric absorbent containing modified MWCNTs and showed that prepared polymeric absorbents containing CNTs had much higher swelling in oil and some organic solvents than those without CNTs. Modified MWCNTs in these polymeric absorbents played triple roles simultaneously: as an adsorbent, a comonomer and a cross-linking agent. In the present study, we designed and prepared new polyelectro- lyte gel, not only successfully incorporating modified MWCNTs, but also more interestingly keeping the high organic solvent absorbency from the low dielectric media to highly polar solvents. For this end, MWCNTs were functionalized with 3-(methacryloyloxy) propyltrimethoxysilane (MPS) and incorporated into the network of polyelectrolyte gel as a cross-linking agent. The effective parameters on compatibility of the Solid State Ionics 257 (2014) 32–37 E-mail address: purjavad@sharif.edu (A. Pourjavadi). 1 Tel./fax: +982 166165311. 0167-2738/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ssi.2013.12.043 Contents lists available at ScienceDirect Solid State Ionics journal homepage: www.elsevier.com/locate/ssi