Synthesis and studies of exceptionally crystalline polyaniline thin films

• Published in: Polymer international 2012-05, Vol.61 (5), p.743-748
• Main Authors: Varma, Sreekanth J, Xavier, Francis, Varghese, Soney, Jayalekshmi, Sankaran
• Format: Article
• Language: English
• Subjects: Applied sciences; Atomic force microscopy; Crystal structure; crystallinity; Direct current; Doping; Electrical resistivity; Exact sciences and technology; Physicochemistry of polymers; polyaniline; Polymer industry, paints, wood; Resistivity; secondary doping; spin-coating; Technology of polymers; Thin films; ultrasonication
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.4131

Highly crystalline camphor sulfonic acid (CSA)‐doped polyaniline (PANI) thin films cast from m‐cresol and N‐methylpyrrolidone (NMP) were investigated. PANI powder prepared by chemical oxidative polymerization subjected to doping–de‐doping–re‐doping procedures was cast into thin films using NMP and m‐cresol as solvents. X‐ray diffraction (XRD) reveals the presence of exceptionally highly crystalline or rather ordered regions in the PANI film samples prepared from m‐cresol. Atomic force microscopy (AFM) images also support the presence of crystalline regions on the surface of these films. The DC electrical conductivity of m‐cresol‐cast PANI is found to be quite high, and much higher than that of NMP‐cast PANI. The free‐carrier absorption tail extending to the near‐infrared region observed in the optical absorption spectrum of the m‐cresol‐cast PANI films suggests a metallic nature and regular structural arrangement in these films. Both inter‐chain and intra‐chain ordering brought about as a result of CSA doping, secondary doping effect of m‐cresol and ultrasonication are suggested to be the prime factors contributing towards the observed excellent crystallinity of these PANI films as evident from the XRD and AFM studies. The marked thermal stability of the m‐cresol‐cast PANI films is also established based on the variation of DC electrical conductivity with temperature and on thermogravimetric analysis. Copyright © 2012 Society of Chemical Industry Ultrasonication and secondary doping with m‐cresol can produce camphor sulfonic acid‐doped polyaniline thin films with excellent crystallinity and very high conductivity.