Effect of the ionic strength on properties of binary alginate/oligochitosan microcapsules

An effect of the ionic strength during the formation of binary alginate/oligochitosan capsules on their properties has been investigated. The increase of sodium chloride concentration leads to the significant decrease of the mechanical resistance and to the increase of the membrane porosity. The pronounced changes of both properties were observed in the same low ionic strength region up to 0.03 M salt concentration. The capsule formation monitoring results indicate a selectivity of the reaction with respect to the length of oligochitosan chains where with increase of the ionic strength, the continuous shift of the complexed oligocations into the direction of higher molar masses was observed. The volumetric extension of the polyanion chains in solution of reduced ionic strength causes more uniform distribution of the chains within the droplet and as the result leads to more homogenous membrane of higher mechanical resistance. (C) 2002 Elsevier Science B.V. All rights reserved.