Characterizing Flux through Micro- and Nanostructured Composites

Abstract

Nano-and microstructured materials differ from bulk materials because they are heterogeneous matrixes with large internal surface area. Interfaces inside nano-and microstructured composites can impact flux of probes through the matrix through unique interfacial chemistry and structure, interfacial binding and repulsion, and interfacial gradients. Gradients in properties are established at the interface between immiscible components; gradients generate forces which can drive flux. In microstructured composites, where a large fraction of molecules moving through the composite are exposed to interfaces and their associated chemistry, structure, and gradients, effects unimportant in homogeneous materials should be considered. First, the relationship between structure and flux can be evaluated by varying the ratio of internal surface area to internal volume of the composite. Structure-flux relationships provide design constraints for forming composite materials. Second, the structure of the interface itself impacts flux. Third, structure-flux relationships will fail as characteristic dimensions of the nanostructure approach molecular dimensions. Examples from the literature are used to illustrate these points.

Polymer electrolytes confined in nanopores: using water as a means to explore the interfacial impedance at the nanoscale

“…Nanocomposites refer to heterogeneous nanostructured materials containing a large internal surface area as compared to the bulk homogeneous material [2]. Dispersing nanometer-size particles throughout the polymer electrolyte is one commonly used method of making such materials [3,4].…”

Electrochemical Effects of Surface-Modified Glass Microspheres in Polyvinylpyridine and Polystyrene Sulfonate Composite Electrodes

“…Composite modified electrodes have been composed of a variety of materials, including polystyrene bead/ion exchange polymer composites, neutron-etched polycarbonate filter/ion exchange polymer composites, conducting polymer/ion exchange polymer composites, , sol−gel/ion exchange polymer composites, , and other polymer/polymer composites. − Modifying electrodes with composites has been used to increase the mass transport through a modifying layer and to increase the physical stability and optical characteristics of the modifying layer . Recently, it has been shown that composite films can also alter the electrochemical selectivity of the electrode …”

Electrochemical Studies of Surface-Modified Glass Bead/Nafion Composites

“…In recent years, researchers have started modifying electrodes with composite films. Composite modified electrodes have been composed of a variety of materials, including polystyrene bead/ion exchange polymer composites, neutron etched polycarbonate filter/ion exchange polymer composites,conducting polymer/ion exchange polymer composites, , sol−gel/ion exchange polymer composites, , and other polymer/polymer composites. − Modifying electrodes with composites has been used to increase the mass transport through a modifying layer and to increase the physical stability and optical characteristics of the modifying layer . Up until now, composite modified electrodes have been used to increase electrochemical flux.…”