dissolving chitosan in 2% acetic acid solution and casting into film.
Generally the dielectric constant of a material arises due to the
polarizations of molecules and the dielectric constant increases with
increase in polarizability. The different types of polarization possible
in a material are (1) electronic polarization (2) atomic polarization
and (3) orientation polarization due to the orientation of dipoles
parallel to the applied field. In heterogeneous materials, there is the
possibility for interfacial polarization which arises due to the
difference in conductivities of the two phases. The time required for
each type of polarization to reach the equilibrium level varies with the
nature of polarization. In the case of chitosan, which is a polar
polymer, at low frequencies all the four types of polarization
contribute towards the dielectric constant. As a result, chitosan
exhibits high dielectric constant, especially at lower frequencies. With
increase in frequency at first the interfacial contribution vanishes
followed by orientation polarization, which in turn reduces the
dielectric constant at higher frequencies. The orientation polarization
requires more time compared to electronic and atomic polarization to
reach static field value. Therefore, at lower frequency region, the
orientation polarization decreases with increase in frequency compared
to electronic and atomic polarizations. The interfacial polarization
generally occurs at much lower frequencies. Nada et al. [20] in
their studies on cellulose/polyethylene glycol (PEG) blends reported
the decrease in dielectric constant with frequency to dielectric
dispersion due to the lag of the molecules behind the alternation of
the electric field at higher frequency. With the incorporation of
chitosan, the crystallinity of the system decreases. As the crystallinity
of the system decreases, the dipoles can orient more easily. The
dielectric constant is related to the resistivity by the equation