Ranjani V. Parthasarathy

Template Synthesis of Electronically Conductive Polymers - A New Route for Achieving Higher Electronic Conductivities

Abstract We have recently developed a method for synthesizing microscopic fibers and tubules of electronically conductive polymers. This method entails synthesis of the polymer within the pores of a microporous host membrane. Conductivities in the narrowest of these “template-synthesized” tubules and fibers can be significantly higher than in conventional forms (e.g. powders or thin films) of the analogous polymer. These previous conductivity data were based on a two-point measurement of the resistance of the host membrane after synthesis of the conductive polymer fibers within this membrane. In this paper we will show results of conductivity measurements on thin films composed of the template-synthesized tubules and fibers. A four-point conductivity measurement was used on these thin films. These four-point measurements corroborate the earlier two-point conductivity data and, again, show that the template-synthesized materials are significantly more conductive.

Electronically conductive polymers as chemically-selective layers for membrane-based separations

Abstract We show that electronically conductive polymers are promising new materials for membrane-based separations, including gas separations and pervaporation. The approach we have taken is to use interfacial polymerization to synthesize thin films of the desired electronically conductive polymer (e.g. polypyrrole, poly(N-methylpyrrole), polyaniline) onto the surfaces of microporous support membranes. These interfacial polymerizations yield thin film composite membranes in which the microporous support provides the requisite mechanical strength and the conductive polymer provides the chemical selectivity. Results of gas-transport and pervaporation experiments on such conductive polymer-based thin film composite membranes will be described.

Enzyme and chemical encapsulation in polymeric microcapsules

Abstract : Polypyrrole microcapsules (prepared via the template method) were used for immobilization of both enzymatic and chemical catalytic systems. Enzymes immobilized include glucose oxidase, catalase, trypsin, subtilisin, and alcohol dehydrogenase. The chemical catalytic system investigated consisted of immobilized Pd nanoparticles for catalysis of hydrogen peroxide decomposition. Microcapsules loaded with glucose oxidase (GOD) were found to have higher enzymatic activity than GOD-loaded thin films, a competing encapsulation method. Trypsin was used to explore the possible leakage of small proteins from the capsules; no leakage was observed. Subtilisin was used to show that these microcapsules can be used in non-aqueous solvents. The effect of capsule wall thickness on the rate of enzymatic reaction was also explored.

Template synthesis of electronically conductive polymers—preparation of thin films☆

Abstract We have recently developed a method for synthesizing micro and nanoscopic fibers and tubules of electronically conductive polymers. This method entails synthesis of the polymer within the pores of a microporous host membrane. Conductivities in the narrowest of these “template-synthesized” tubules and fibers can be significantly higher than in conventional forms ( eg powders or thin films) of the analogous polymer. These previous conductivity data were based on a two-point measurement of the resistance of the host membrane after synthesis of the conductive polymer fibers within this membrane. In this paper we will show results of conductivity measurements on thin films composed of the template-synthesized tubules and fibers. A four-point conductivity measurement was used on these thin films. These four-point measurements corroborate the earlier two-point conductivity data and, again, show that the template-synthesized materials are significantly more conductive.

High Pressure Conductivity Study of Template Synthesized Polypyrrole: Observation of a Crossover from Three to One Dimensional Variable Range Hopping.

Abstract We have studied thin films of thin and thick wall template synthesized polypyrrole microtubules. We observe a crossover from three- to one-dimensional variable range hopping in our samples at low temperatures. Our results clearly indicate that the geometry of the microtubules has an influence on the conductivity. The transition temperature from three- to one-dimensional variable range hopping shifts to lower temperatures when high pressure is applied. The results are discussed on the basis of the geometry of the microtubules.