Please cite this article in press as: N. Velhal, et al., Studies on galvanostatically electropolymerised polypyrrole/polyaniline composite thin films on stainless steel, Appl. Surf. Sci. (2014), http://dx.doi.org/10.1016/j.apsusc.2014.03.180 ARTICLE IN PRESS G Model APSUSC-27581; No. of Pages 7 Applied Surface Science xxx (2014) xxx–xxx Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Studies on galvanostatically electropolymerised polypyrrole/polyaniline composite thin films on stainless steel Ninad Velhal, Narayan Patil, Shivaji Jamdade, Vijaya Puri ∗ Thick and Thin Film Device Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, India a r t i c l e i n f o Article history: Received 30 October 2013 Received in revised form 24 March 2014 Accepted 27 March 2014 Available online xxx Keywords: Polypyrrole Surface morphology Electropolymerisation Microwaves a b s t r a c t The polypyrrole/polyaniline composite thin films were prepared by a simple electrodepositon technique on stainless steel substrate. The FT-IR spectra confirm the formation of polypyrrole/polyaniline compos- ite structure; the surface morphology showed that polypyrrole/polyaniline has cauliflower like structure in 90–10% composite whereas there is drastic change in morphology in the 50–50% composite. The microwave properties such as reflection, absorption, dielectric behavior of polypyrrole/polyaniline com- posite thin films with frequency were studied in the frequency range 13–18 GHz. The thickness, DC and microwave conductivity were also studied. The dielectric constant and microwave conductivity showed higher value in the 70–30% composite thin film. © 2014 Elsevier B.V. All rights reserved. 1. Introduction In electronic industries there is a requirement of large area and smart surfaces at which the high frequency electromagnetic transmittance, reflectance can be controlled. This may be done by using the conducting polymers [1]. The conducting polymers have emerged as a new class of materials in the last few decades, because of their excellent electrical and mechanical properties such as high conductivity, electrical properties, ease of synthesis and ease of production etc. Recently, conducting polymer composites have also received tremendous attention and it has become one of the most active and promising research areas [2]. These conducting polymer composites are attractive due to their potential applications in rechargeable batteries [3,4], shielding of electromagnetic interfer- ence [5], microwave and radar absorbing materials [6], sensors [7,8], electronic and bioelectronics components [9], membranes [10], electrochemical capacitors [11], electro chromic device [12], light-emitting devices [13], antistatic [14] and anticorro- sion coatings [15], etc. Among the various conducting polymers, polypyrrole and polyaniline are the most stable polymers with good mechanical, electrical properties which can enhance the utility of stainless steel [16,17]. Stainless steel is a cost effective and useful material in the radio frequency and microwave region. It is used for the fabrication of ∗ Corresponding author. Tel.: +91 9766420162. E-mail addresses: vijayapuri1@gmail.com, vrp phy@unishivaji.ac.in (V. Puri). the antennas which is used in radio astronomy, remote sensing and communication purposes. The modification of the surface properties of stainless steel may lead to better performance of the antenna structure [18]. In this paper we report the properties of polypyrrole/polyaniline composite thin films deposited by electropolymerisation technique on stainless steel substrate. 2. Experimental Pyrrole monomer (Aldrich), aniline monomer (Aldrich), p- toluene sulfonic acid (PTSA) (Merck) was used as received, while water was distilled before use. Monomer solution was prepared by dissolving pyrrole (0.7 ml) and aniline (2.5 ml) in 100 ml distilled water and p-toluene sulfonic acid (1.735 gm) in 100 ml distilled water. Ratio of pyrrole and aniline was changed by (90–10)%, (70–30)% and (50–50)% with constant dopant concentration i.e. 5%. The thin sheet of stainless steel (SS) of thickness ∼0.5 mm was cut to the size of 1.1 × 2 cm. These dimensions were according to the size of the substrate holder of the microwave set up. Prior to the electrodepositon, the substrates were polished to a smooth surface finish using finer grades of polish papers, washed with soap solution and distilled water and dried under a hot air stream and wiped by lint less tissue paper. The electrodepositon setup consisted of work- ing, counter and reference electrode attached to bakelite holder. A saturated calomel electrode was used as a reference electrode and high density and high surface area graphite rod was used as the counter electrode. The current density was 1.3 mA/cm. An adher- ent black colored composite film was deposited on the stainless steel (SS) substrate at the ratio (90–10)%. As aniline percentage http://dx.doi.org/10.1016/j.apsusc.2014.03.180 0169-4332/© 2014 Elsevier B.V. All rights reserved.