Dielectric properties of slightly hydrated collagen: time-water content superposition analysis

The frequency dependences of the dielectric constant, ε′, and the loss factor, ε″, in collagen were measured at several water contents from 0.1 to 0.3 g/g collagen over a frequency range of 30 Hz to 100 kHz and at a temperature of 20°C. Remarkable dispersion was observed at the lower frequencies for higher water contents. According to accumulated results on the thermodynamic and structural investigations, the dispersion has some analogy to the surface conduction proposed by B. V. Hamon (1953) Aust. J. Phys. 6 , 304–315]. An empirical relation bewteen ε″ and frequency, f, ε″ ∝? fⁿ, where 0 < n < 1, suggests that the dielectric and conductive properties of hydrated collagen are related to carrier jumps between neighboring sites. For the polarization mechanism of this dispersion, we supposed a model of the transfer of protons between absorbed water molecules, and found that the time–water content superposition procedure is applicable to slightly hydrated collagen. The results derived from the superposition procedure show that the water content, ?, is related to the conductivity, σ, or the dielectric loss factor by the following equations: σ (?, f) = const. × ?^nm?1f^1?n and ε″ (?, f) = const. ?^nmf^?n, respectively, where m is a constant independent of ? and f. These results agree with that derived by another treatment of the same data. The role of water molecules in the conduction and polarization in slightly hydrated collagen is considered to be not far from that assumed in the model.