| Abstract
| - Nano- and microstructured materials differ from bulk materials because they are heterogeneous matrixeswith large internal surface area. Interfaces inside nano- and microstructured composites can impact fluxof probes through the matrix through unique interfacial chemistry and structure, interfacial binding andrepulsion, and interfacial gradients. Gradients in properties are established at the interface betweenimmiscible 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 theirassociated chemistry, structure, and gradients, effects unimportant in homogeneous materials should beconsidered. First, the relationship between structure and flux can be evaluated by varying the ratio ofinternal surface area to internal volume of the composite. Structure−flux relationships provide designconstraints 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 approachmolecular dimensions. Examples from the literature are used to illustrate these points.
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