Dhana Lakshmi

One-Dimensional Polyaniline Nanotubes for Enhanced Chemical and Biochemical Sensing

In this work we explored a simple, cheap and fast route to grow polyaniline (PANI) nanotubes arranged in an ordered structure directly on an electrode surface by electrochemical polymerisation. The deposited nanostructures were electrochemically and morphologically characterised and then used as a functional substrate for biochemical sensing by combining the intrinsic advantages of nanostructures as optimal transducers and the well known benefits of molecularly imprinted polymers (MIPs) as receptors. The hybrid nanostructured-MIP sensor was applied to the molecular recognition of catechol. Moreover, a gas sensing application was also investigated by exploiting resistance variation of the polymer in presence of different gases (CO, NO2, NH3 and ethanol).

Microplates with Adaptive Surfaces

Here we present a new and versatile method for the modification of the well surfaces of polystyrene microtiter plates (microplates) with poly(N-phenylethylene diamine methacrylamide), (poly-NPEDMA). The chemical grafting of poly-NPEDMA to the surface of microplates resulted in the formation of thin layers of a polyaniline derivative bearing pendant methacrylamide double bonds. These were used as the attachment point for various functional polymers through photochemical grafting of various, for example, acrylate and methacrylate, polymers with different functionalities. In a model experiment, we have modified poly-NPEDMA-coated microplates with a small library of polymers containing different functional groups using a two-step approach. In the first step, double bonds were activated by UV irradiation in the presence of N,N-diethyldithiocarbamic acid benzyl ester (iniferter). This enabled grafting of the polymer library in the second step by UV irradiation of solutions of the corresponding monomers in the microplate wells. The uniformity of coatings was confirmed spectrophotometrically, by microscopic imaging and by contact angle measurements (CA). The feasibility of the current technology has been shown by the generation of a small library of polymers grafted to the microplate well surfaces and screening of their affinity to small molecules, such as atrazine, a trio of organic dyes, and a model protein, bovine serum albumin (BSA). The stability of the polymers, reproducibility of measurement, ease of preparation, and cost-effectiveness make this approach suitable for applications in high-throughput screening in the area of materials research.

Conductive Polymers for Plastic Electronics

Since the discovery of conductive polymers, scientists have devoted great efforts to successfully synthesizing conductive polymers, which combine the processing and mechanical properties of “conventional insulating polymers” with the electrical and optical properties of metals. Nowadays the use of conductive polymers in commercial products is still limited, due to the partial success achieved in producing materials with high conductivity and real plastic characteristics. Once better conductive plastics are developed, the potential applications can be endless, ranging from organic bioelectronics to plastic electronic components for sensors and biosensors. The difficulty in trying to process conductive polymers using the methods normally utilized by the polymer industry (e.g., injection molding) arises from the fact that these materials are not intrinsically thermoplastic. Over the last two to three decades, scientists have tried different approaches to produce thermoplastic polymers with high conductivity. In this chapter, after a brief history of conductive polymers, these approaches are reviewed, with particular emphasis on polyaniline. A section that describes micro-injection molding and highlights the thermoplastic characteristics required by the material used for the process is also included. Finally, possible improvements of such materials (e.g., molecular recognition) achieved by applying the molecular imprinting technology are also mentioned.