Macromolecular Nanotechnology Processable polyaniline suspensions through in situ polymerization onto nanocellulose Nguyen Dang Luong a , Juuso T. Korhonen b , Antti J. Soininen b , Janne Ruokolainen b , Leena-Sisko Johansson c , Jukka Seppälä a,⇑ a Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University, School of Chemical Technology, P.O. Box 16100, FI-00076 Aalto, Finland b Molecular Materials, Department of Applied Physics, Aalto University, School of Science, P.O. Box 15100, FI-00076 Aalto, Finland c Forest Products Surface Chemistry Group, Department of Forest Products Technology, Aalto University, School of Chemical Technology, P.O. Box 16300, FI-00076 Aalto, Finland article info Article history: Received 16 July 2012 Received in revised form 16 October 2012 Accepted 28 October 2012 Available online 23 November 2012 Keywords: Polyaniline Nanofibrillated cellulose Conducting polymers Nanocomposites abstract Polyaniline-based aqueous suspensions containing a variety of polyaniline (PANi) contents ranging between 5 and 80 wt.% have been successfully developed through in situ polymer- ization of aniline in a nanocellulose suspension. Herein, a suspension of high aspect ratio nanofibrillated cellulose (NFC), which was prepared by combining an enzymatic hydrolysis and mechanical shearing, was utilized as platform, stabilizer, and reinforcement for PANi deposition during the in situ synthesis. As a demonstration for the good processability, NFC/PANi composite paper-based materials which exhibited good mechanical properties and high conductivity were easily fabricated from these NFC/PANi suspensions. The NFC/ PANi composite paper exhibits a percolation threshold of electrical conductivity of 4.57 vol.% of PANi content, at which the corresponding conductivity was measured to be 2.6  10 5 S cm 1 , which is well above the antistatic criterion of 10 8 S cm 1 . Remarkably, at the percolation threshold, the mechanical strength of the NFC/PANi composite paper is as same as that of neat NFC. This work provides a straightforward procedure for fabrication of PANi-based suspensions and flexible paper-like materials with good mechanical and electrical properties, which may find potential applications in flexible electrodes, antistatic coatings, and electrical conductors. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Polyaniline is one of the most studied conducting poly- mers recently owing to its relative ease of synthesis, tun- able properties, low cost of monomer, and better environmental stability compared to other conducting polymers [1]. PANi can be synthesized via a numerous chemical [2] or electrochemical polymerizations [3]. Upon chemical doping and oxidation/reduction processes, elec- trical conductivity of PANi is commonly adjusted in a range of 10 8 –10 2 Sm 1 [1]. Because of many advantages, PANi has been studied for various applications, such as supp- ercapacitors [4], batteries [5], chemical and biological sen- sors [6,7], electrical conductors [8], tissue engineering scaffolds [9], and antistatic coatings [10]. However, the dif- ficulties in processing of PANi into films and paper-like materials, very low solubility in most of the available solvents, and its relatively poor mechanical properties decrease its performances and utilities in many applications, especially when it is used as an antistatic coating or in flex- ible devices. Therefore, significant efforts have been done in preparation of composites and blends of PANi with other conventional polymers that have good physical properties, such as polystyrene (PS) [11], polyamide [12], and polysac- charide [13], in order to increase PANi’s processability and mechanical performances [14]. The processability of PANi 0014-3057/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2012.10.026 ⇑ Corresponding author. Tel.: +358 9 470 22614; fax: +358 9 451 2622. E-mail address: jukka.seppala@aalto.fi (J. Seppälä). European Polymer Journal 49 (2013) 335–344 Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY