Sensors and Actuators A 220 (2014) 249–261 Contents lists available at ScienceDirect Sensors and Actuators A: Physical j ourna l h o mepage: www.elsevier.com/locate/sna Electromechanical properties study of 1-butyl-3-methylimidazolium chloride/cellulosic gel blended with polydiphenylamine Wissawin Kunchornsup, Anuvat Sirivat ∗ The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand a r t i c l e i n f o Article history: Received 30 December 2013 Received in revised form 13 October 2014 Accepted 16 October 2014 Available online 27 October 2014 Keywords: Electromechanical responses Cellulose 1-Butyl-3-methylimidazolium chloride (BMIMCl) Ionic liquids Polydiphenylamine (PDPA) Actuator a b s t r a c t 1-Butyl-3-methylimidazolium chloride (BMIMCl) is an ionic liquid utilized as an effective cellulose gelling agent for the fabrication of electro-responsive cellulose. The cellulose electromechanical properties are primarily dependent on the ionic polarization of BMIM + and its mobility. This work focuses on the syner- gism between the ionic contribution of ionic liquid/cellulosic gel (CelGel) and the electronic contribution of a conductive polymer, polydiphenylamine (PDPA) of various doping levels and concentrations (%v/v) under electrical actuation. Initially, CelGel is blended with doped PDPA of various doping levels. At 2.50%v/v, the CelGel blend exhibits the highest electrical conductivity of 21 S/cm at a 10:1 PDPA doping level. This results from proton conduction and electron delocalization which are intrinsically present within the doped PDPA embedded in the blends. Higher PDPA doping level in the blends produces lower storage modulus sensitivity. This suggests that the higher doping levels of PDPA create a higher degree of short-range ionic polarization, thus retarding BMIM + mobility and lowering storage modulus sensitivity. The %v/v of undoped PDPA (uPDPA) in the blends is further investigated with a %v/v variation between 0.01%v/v and 7.50%v/v. A larger amount of uPDPA in the blend provides a larger electrostatic binding interaction between BMIM + and Cl - counterion, and this diminishes the storage modulus sensitivity as well. With a higher amount of uPDPA added, the bending angle also diminishes due to the electrostatic binding interaction. However, the optimal %v/v of uPDPA is 0.01%v/v, the ionic-electronic synergism produces the highest non-symmetric swinging angle of 77 ◦ accompanied with dielectrophoresis and electrophoresis force of 8.25 mN. This condition allows a number of polarizable domains on uPDPA with less rigidity on the CelGel relative to the pristine CelGel. The results suggest that uPDPA is a potential conductive polymer candidate for producing tailor-made electromechanical responses at optimal %v/v in the categories of ionic gels and dielectric elastomers. © 2014 Published by Elsevier B.V. 1. Introduction Cellulose consists of -(1→4)-linked glucose repeating units [1], whose piezoelectric properties are attributed to the internal rota- tion of the polar atomic groups associated with asymmetric carbon atoms based on non-centro symmetry that are required for actu- ation [2]. However, this limits the dissolution of cellulose via the strong inter- and intra-molecular hydrogen bonding of the cellu- losic hydroxyl groups. Ionic liquids (ILs) are salts composed of organic nitrogen, inor- ganic cations, and inorganic anions. Swatloski et al. [3] pioneered the dissolution of a cellulose in 1-butyl-3-methylimidazolium chloride (BMIMCl). This dissolution system provided processing ∗ Corresponding author. Tel.: +66 2 218 4131; fax: +66 2 611 7221. E-mail address: anuvat.s@chula.ac.th (A. Sirivat). advantages, namely high solubility at a suitable temperature, 10 wt% solubility at 100 ◦ C without derivatization, and less chain degradation [4]. When the amount of hydroxyl groups in the gel is attained with highest dissolution without degradation, the gel will exhibit effective actuation via electronic polariza- tion. In addition, certain members of the IL family possess the requirements for electrochemical devices—high ionic conductivity (>10 -4 S cm -1 ); large electrochemical windows (>1 V), in which the electrolyte is neither reduced nor oxidized at an electrode; fast ion mobility during redox events (>10 -14 m 2 V -1 s -1 ); low volatility; and environmental stability [5]. Nafion swollen in 1-ethyl- 3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-IM) was studied and shown that the actuation speed and the ionic conductivity increased with increasing counterion size and increasing IL content, due to the counterions of the polymer acting as the primary charge carriers [6]. The use of 1-ethyl- 3-methylimidazoliumtrifluoromethanesulfonylimide IL was then http://dx.doi.org/10.1016/j.sna.2014.10.019 0924-4247/© 2014 Published by Elsevier B.V.