Conducting polymers: novel materials for chemical and bio-sensors

Conducting polymers are novel organic semiconducting materials with promise in a wide range of electronic applications from charge storage to sensors. The electronic and optical properties of these polymers are very sensitive to their chemical and electrochemical state, with conductivities changing by several orders of magnitude in response to small changes in the chemical/electrochemical state. This property has been exploited to develop sensors, and electronic switching devices. Some of the progress in this direction is described here with specific reference to work done at IIT, Bombay

Electrochemistry of polyaniline Langmuir–Blodgett films

Langmuir–Blodgett (LB) manipulation of polyaniline has been variously employed to obtain organized assemblies for use in molecule-based electronic devices. However, the electrochemical characteristics of polyaniline LB films which have a direct implication on the proposed device applications have not been given much attention. We report here, electrochemical characterization of multilayer LB films of polyaniline prepared by employing N-methylpyrrolidone as the processing solvent. The films have been transferred onto a variety of substrates such as quartz, platinum, platinum sputtered on quartz, and conducting tin oxide on glass. The electrochemistry of polyaniline LB films has been studied using cyclic voltammetry coupled with a quartz crystal microbalance (QCM). Cyclic voltammograms were obtained for films transferred at different surface pressures, for films containing different number of layers. The electrochemical characteristics of LB multilayers were compared with those of electrochemically deposited films and were used to infer the packing behaviour of polymer chains in the LB film structure. It was found that multilayer LB films are electroactive but the kinetics of counter ion transport in these films is slower than that observed in electrochemically deposited films. The multilayer LB films also show poor electrochromic switching behaviour.© Elsevie

Preparation and characterization of mixed LB films of polyaniline and cadmium arachidate

Langmuir isotherms of mixed monolayers of polyaniline and cadmium arachidate have been studied, and mixed monolayers have been transferred uniformly onto substrates as Langmuir-Blodgett (LB) multilayers. The LB films were characterized by XRD, W-Vis and FTIR spectroscopy, de conductivity and cyclic voltammetric measurements. The FTIR results suggest that the films contain arachidate salt, and the XRD results indicate the presence of a layered structure in the mixed LB films. (C) 1997 Elsevier Science S.A

A study of Langmuir and Langmuir-Blodgett films of polyaniline

Formation of a stable monolayer of polyaniline (EB) at the air-water interface has been obtained, employing N-methylpyrrolidone (NMP) as processing solvent. Surface pressure-mean molecular area isotherm and compressibility of the polyaniline monolayer were studied under different subphase conditions such as the subphase temperature, the subphase pH, and the nature of counterions in the subphase. The mean molecular area found and compressibility results have been interpreted in terms of the rigidity of the polymer chains at the air-water interface. Further, polyaniline monolayers have been transferred onto different substrates and the multilayers were characterized by spectroscopic, electrical, and electrochemical techniques. The Langmuir-Blodgett multilayers were also deposited at different surface pressures. The transfer behavior and the electrochemical characteristics of these films indicate differences in their packing arrangement

Conducting Polymer Nanomaterials and Their Applications

A paradigm shift takes place in the fabrication of conducting polymers from bulky features with microsize to ultrafine features with nanometer range. Novel conducting polymer nanomaterials require the potential to control synthetic approaches of conducting polymer on molecular and atomic levels. In this article, the synthetic methodology of conducting polymer has been briefly considered with chemical oxidation polymerization and electrochemical polymerization. The recent achievements in the fabrication of conducting polymer nanomaterials have been extensively reviewed with respect to soft template method, hard template method and template-free method. It also details the morphological spectrum of conducting polymer nanomaterials such as nanoparticle, core-shell nanomaterial, hollow nanosphere, nanofiber/nanorod, nanotube, thin film and nanopattern and nanocomposite. In addition, their applications are discussed under nanometer-sized dimension.This work has been financially supported by the Brain Korea 21 program of the Korean Ministry of Education and the Hyperstructured Organic Materials Research Center supported by Korea Science and Engineering Foundation