Complex impedance spectroscopy to investigate degradable chondroitin-poly(amino-serinate) complexes

ABSTRACT

Sodium chondroitin-4-sulfate and poly(amino-serinate) bromide can interact to form a degradable polyelectrolyte complex. The structure of each polymer and of their complex before and after degradation is investigated by complex impedance spectroscopy. Poly(amino-serinate) bromide and sodium chondroitin-4-sulfate exhibit dc conductivity and dielectric relaxation phenomena in the 102e106 Hz range. On the contrary, no dc conductivity and dielectric relaxation are observed in the polyelectrolyte complex before degradation. After degradation, the released chondroitin-4-sulfate is re-complexed with additional poly(amino-serinate) bromide. Contrary to the original parent complex the restored complex exhibits both dc conductivity and dielectric relaxation phenomena. This difference is assigned to structural defects due to the presence of residual poly(amino-serinate) oligomers which compete with the newly added poly(amino-serinate) to complex the released chondroitin-4-sulfate. This outcome is interpreted assuming the displacement of the low molecular by higher molecular weight chains in contrast to the behavior usually reported for this type of polymeric systems.