Effects of Solvent Interactions on the Structure and Properties of Prepared PAni Nanofibers Sujata Pramanik, 1 Niranjan Karak, 1 Somik Banerjee, 2 Ashok Kumar 2 1 Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, Tezpur, Assam 784028, India 2 Material Research Laboratory, Department of Physics, Tezpur University, Tezpur, Assam 784028, India Received 28 July 2011; accepted 3 February 2012 DOI 10.1002/app.36950 Published online in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: The changes of structure and properties of nanofibers were studied as a function of solubility param- eters of the organic solvents that are used in interfacial polymerization of polyaniline (PAni) nanofibers. The pres- ence of UV–visible absorbance at 340, 440, and 800 nm confirmed the formation of emeraldine salt structure of the prepared PAni nanofibers. Fourier transform infrared spectral results indicate an increasing trend of benzenoid to quinoid ratio with the decrease of interaction of the sol- vents with aniline. This can be correlated to the increase in the degree of conjugation of the polymer chain. Photolu- minescence study revealed an increase in the density of defect state with the decrease of interaction. Single-line approximation technique was used to analyze the broad- ening of the most intense X-ray reflection peak corre- sponding to (110) plane of the nanofibers. The greater the solvent–monomer interaction, the lesser was the domain length and p-stacking of the PAni chains. The study of this interaction is instrumental to precisely control the internal conformation of the PAni nanofibers. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2012 Key words: polyaniline nanofiber; structure and properties; photoluminescence; FTIR INTRODUCTION Among the family of p-conjugated polymers, polyani- line (PAni) carves a unique niche because of its unique properties such as good environmental stability, solu- bility, and simple acid/base doping/dedoping chemis- try. PAni is a promising material for a wide range of applications, namely, anticorrosion coatings, 1 batteries, 2 potentiometric sensors, 3 separation membranes, 4 anti- static coatings, 5 and fluorescent sensing for nucleic acid detection. 6 PAni nanofibers possess similar functional- ities as the bulk counterpart; however, the former proves to be a better potential for chemical sensing and water dispersability than the latter. 7 Recently, scientists have focused attention on one- dimensional PAni nanostructures, such as nanofib- ers, nanotubes, and nanorods, because of their low dimensional structures, organic nature, and metal- like conductivity. 8 Various strategies have been developed for the synthesis of one-dimensional PAni nanostructures by introducing ‘‘structure directing agents,’’ which include surfactants, 9 liquid crystals, 10 polyelectrolytes, 11 nanowire seeds, 12 aniline oligmers, 13 and relatively complex bulky organic dopants 14 during the polymerization process. Jing et al. 15 used ultrasonic synthetic approach to synthe- size PAni nanofibers. Li and Wang 16 fabricated chi- ral PAni nanofibers using an aniline oligomer to accelerate the polymerization reaction. Zhang et al. 17 documented a ‘‘nanofiber seeding’’ method to syn- thesize bulk quantity of PAni nanofibers in one step. Lu et al. 18 reported the preparation of PAni nanofib- ers by using a ‘‘high-gravity oxidative polymeriza- tion’’ in a rotating packed bed. In addition, Huang et al. 5,19 reported a route to synthesize PAni nanofib- ers at the organic/inorganic interface. Among these reported approaches, interfacial polymerization developed by Huang and Kaner 9 is the most facile as well as template-free approach to synthesize PAni nanofibers. The interfacial polymerization technique yields high-quality PAni nanofibers. The secondary overgrowth is restricted as the hydrophilic nanofib- ers move toward the aqueous phase leaving the interface for directional polymerization reaction. The relative ease of interfacial polymerization made it the preferred technique in many fields ranging from microencapsulation of pharmaceutical products to the synthesis of conducting polymers. 20,21 Although Correspondence to: N. Karak (karakniranjan@yahoo.com). Contract grant sponsors: The authors express their gratitude and thanks to the research project assistant given by DRL, India, through the grant no. DRL/1047/TC, dated 2nd March, 2011, SAP (UGC), India through grant No. F.3-30/2009(SAP-II) and FIST program-2009 (DST), India through the grant No.SR/FST/CSI-203/209/1 dated 06.05.2010. SAIF, NEHU, Shillong, is acknowledged for TEM imaging. Journal of Applied Polymer Science, Vol. 000, 000–000 (2012) V C 2012 Wiley Periodicals, Inc.