Preparation and rheological properties of deoxycholate-chitosan and carboxymethyl-chitosan in aqueous systems

Self-aggregation and micelles of amphiphatic polymers are important functions in application, and their properties are influenced by the parent hydrophilic polymer and the hydrophobic groups. In this paper, deoxycholate-chitosan (DE-chitosan) and carboxymethyl-chitosan (CM-chitosan) were prepared from chitosan (MW, 28 kDa; DD, 90%). The effects of acid, pH and ionic concentrations on aggregation behaviors of the polymers in aqueous systems were measured, respectively. The ionic strength was found to enhance the aggregation of DE-chitosan, but had no influence to CM-chitosan and chitosan itself. The modification of hydrophobic groups and hydrophilic groups influenced the rheology properties of both parent chitosan and the derivatives. The assemblage of DE-chitosan in solution can be controlled by an oil/water (methylene chloride/DE-chitosan solution) emulsification process using methylene chloride. The micelles of DE-chitosan formed nano-micelles particles of 200-600 nm in diameter which can be used to encapsulate lipid-soluble compounds for drug dispersing and delivery releasing.