Dielectric analysis of chitosan gel beads suspensions: Influence of low crosslinking agent concentration on the dielectric behavior

Dielectric measurements were carried out for the suspensions of chitosan gel beads (CGB) crosslinked with glutaraldehyde (GA), ranging in crosslinking time from 1 to 180 min at six fixed low GA concentrations over a frequency range from 40 to 110 MHz. The distinct dielectric relaxations observed in the frequency range of 104–105 Hz were explained by the effects of the interfacial polarization. By fitting the experimental data with Cole-Cole equation the dielectric parameters of the suspensions were obtained, and the phase parameters were calculated using Hanai's method. The influence of crosslinking on the dielectric spectra of CGB was investigated by viewing the crosslinking time dependencies of conductivity increment (Δκ  ), relaxation frequency (f0f0), permittivity of CGB (εiεi), conductivity of CGB (κiκi) and conductivity of continuous media (κaκa) at six fixed GA concentrations. Some information were gained, such as, thinner electric double layer, particle with rougher surface and more compact gel backbone with increasing crosslinking time. The basic information obtained can provide valuable references for the preparation of CGB and the application to more extensive fields such as controlled-release technology of medicament.

Three-dimensional representations of the crosslinking time dependency of (a) the permittivity spectrum and (b) the conductivity spectrum for the suspensions of CGB crosslinked at GA concentration of 0.300% for different crosslinking times. The ε/κε/κ axis is linear and f/tf/t axis is logarithmic.Figure optionsDownload as PowerPoint slide