Development of environmental friendly castor oil-based waterborne polyurethane dispersions with polyaniline T. Gurunathan a,b *, Ravi Arukula b , Jin Suk Chung a and Chepuri R.K. Rao b This study describes the fabrication and characterization of castor oil-based waterborne polyurethane/polyaniline (COWPU/PAni) conducting polymer blend films. The COWPU synthesized from isophorone diisocyanate was reacted with castor oil to form prepolymers, which were chain extended by reacting it with N-methyldiethanolamine. Quaternization and self-emulsification including deionized water followed in COWPU dispersions. Also, COWPU/PAni hybrid dispersions were synthesized with 2, 4, and 6 wt% of PAni–dodecyl benzene sulfonic acid to make different conductive composites. The outcome of COWPU/PAni was characterized by Fourier transform infra- red spectrometer, differential scanning calorimeter, thermogravimetric analysis, dynamic mechanical and thermal analyzer, and scanning electron microscopy analysis. According to Fourier transform infrared spectrometer analysis, hydrogen bonding appears between –NH of PAni and C¼O of COWPU. Meanwhile, incorporating PAni can improve the thermal stability of COWPU. The resulting COWPU/PAni conducting blend films can be used as antistatic and an- ticorrosive coating materials. Copyright © 2016 John Wiley & Sons, Ltd. Keywords: castor oil; polyurethane; polyaniline; waterborne polyurethane; conducting blend film INTRODUCTION Waterborne polyurethane (WPU) has earned increasing aware- ness for its overall balance of resources and environmental friendliness. In particular, WPU has merged with new chemical technology for eco-friendly coatings and adhesive. [1,2] However, the water resistance, relatively low heat resistance, weak adhesion in the moist environment, mechanical properties, and thermal stability of WPU films are still lesser to those of solvent-based polyurethane (PU). [3] To overcome these draw- backs, several modifications have been investigated like starch, [4] casein, [5] silica, [6] and organosilicon. [7] Commercial WPU can be accessed from the reaction of a diisocyanate with a polyol and a hydrophilic chain extender obtained from petroleum-based sources. However, limited fossil resources will be affably dimin- ished within a few generations. Consequently, the petroleum- based material with renewable resources establishes a critical contemporary challenge in both economic and environmental aspects. [8] Vegetable oils are one of the accepted, abundant biological sources and significant renewable raw materials to obtain different outcomes with a large variety of opportunities in the chemical and polymer industries. [9–13] Vegetable oil-based PU is usually assembled from chemically modified triglycerides and their fatty acids. The composition and characteristics of the resulting PU thermosets enormously depend on the type of triglyceride used, [14] the quality of the iso- cyanate group, [15] and the level of crosslinking. [16] As an out- come of the hydrophobic nature of triglycerides, PU derived from vegetable oils exhibit excellent chemical and physical prop- erties, including improved hydrolytic tendencies and thermal stability. [17] Recently, environmental friendly cationic PU disper- sions have been strongly prepared by the reaction of diisocyanates and polyols from castor oil (CO), [18] soybean oil, [19,20] and rapeseed oil. [21] The emerging PU films, contain- ing 50–70 wt% vegetable oil polyol as a renewable resource, show thermo-physical and mechanical properties similar to PUs from petroleum-based polyols, proposing various hopeful applications for novel environmental-friendly, bio-based materials. [2] Among the group of conducting polymers, polyaniline (PAni) appears to be the most likely competitor because of its unusual redox property as well as it can be readily synthesized. [22,23] The general description for perfect PAni in their primary structures consists of three (C 6 H 4 NH) benzenoid links and one (N¼C 6 H 4 ¼N) quinoid link . [24,25] PAni has been utilized for various purposes including corrosion protection. [26] MacDiarmid et al. [27] was the first one who proposed corrosion assurance by intrinsically conductive polymer. In contradiction to PU, PAni doped with simple mineral acids is not processable, and a twofold advantage is required when both are blended. [28] The best method of mixing PAni is to integrate this polymer in an aqueous dispersion and later mixing it into waterborne PU. [29] Moreover, the interplay between –NH in PAni and –NHCOO in PU may be a bonus to enhance the adaptability of the system. [30] Yoshikawa et al. [31] also * Correspondence to: Thangavel Gurunathan, School of Chemical Engineering, University of Ulsan, Namgu, Daehakro 93, Ulsan 680-749, Korea. E-mail: juru001@gmail.com a T. Gurunathan, J. Suk Chung School of Chemical Engineering, University of Ulsan, Namgu, Daehakro 93, Ul- san 680-749, Korea b T. Gurunathan, R. Arukula, C. R.K. Rao Polymers and Functional Materials Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India Short communication Received: 13 January 2016, Revised: 22 February 2016, Accepted: 23 February 2016, Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pat.3797 Polym. Adv. Technol. (2016) Copyright © 2016 John Wiley & Sons, Ltd.