Several diacetylenic lecithins form tubular microstructures (tubules) when their liposomes are cooled through the chain-melting transition. Recently, the tubules have been metal plated by an electroless technique. This paper reports on the interaction of permalloy coated tubules with electromagnetic radiation. At 10 vol % loading of tubules in an epoxy matrix has a real dielectric constant ε′≊50 at a frequency of 9.5 GHz. Simple electrodynamics accounts well for the observed results. Far higher values of ε′ may be achievable with longer tubules and with improved metal coatings.
Measurements have been made of the dielectric response of distributions of metallized fibers aligned in epoxy matrices for different loading fractions and fiber lengths. These have been shown to be in reasonable agreement with a simple independent particle theory. Use of the theory allows classification of fiber dielectric behavior by fiber conductivity and a characteristic length. Some aggregation of the fibers has been observed, even at relatively low loading densities. Computer simulation suggests enhanced dielectric constants of the composites for a moderate range of separations where the fibers are offset about 75% of their lengths with respect to each other and are closer than about 10 radii. This effect may be significant for aligned fibers which tend to aggregate in the magnetic field with separations and offsets within this range. The resulting composites are rugged and easily machined, and with less than 5% fiber weight loading have large, highly anisotropic dielectric constants of 60 or more at microwave frequencies in the X band. In conjunction with their (predicted) broadband performance characteristics such media should prove useful for a variety of applications.
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